Integrated combustion reactors and methods of conducting simultaneous endothermic and exothermic reactions

ABSTRACT

Integrated Combustion Reactors (ICRS) and methods of making ICRs are described in which combustion chambers (or channels) are in direct thermal contact to reaction chambers for an endothermic reaction. Particular reactor designs are also described. Processes of conducting reactions in integrated combustion reactors are described and results presented. Some of these processes are characterized by unexpected and superior results, and/or results that can not be achieved with any prior art devices.

OTHER APPLICATIONS

[0001] The invention may be further understood by reference to U.S.patent applications Ser. Nos. ______ (Title: Multistream MicrochannelDevice; Attorney Docket No. 02-001), ______ (Title: Process for Coolinga Product in a Heat Exchanger Employing Microchannels for the Flow ofRefrigerant and Product, Attorney Docket No. 01-002), and ______ (TitleProcess for Conducting an Equilibrium Limited Chemical Reaction in aSingle Stage Process Channel; Attorney Docket No. 02-051), all of whichwere filed on Aug. 15, 2002, all of which are incorporated herein byreference.

INTRODUCTION

[0002] Currently, endothermic reactions performed in microreactors aredriven using heat from an external source, such as the effluent from anexternal combustor. In doing so, the temperature of the gas streamproviding the heat is limited by constraints imposed by the materials ofconstruction. For example, a typical microreactor constructed fromInconel 625 might be limited in use for gas service to temperatures of˜1050° C. or less. Practically, this means that the effluent from anexternal combustor must be diluted with cool gas (i.e. excess air) tobring the gas temperature down to meet material temperature constraints.This increases the total gas flow rate, raising blower/compressor costs.Moreover, heating the gas stream externally introduces heat losses(associated with delivery of the hot gas to the microreactor) andexpensive high temperature materials to connect the combustor to themicroreactor.

[0003] On the other hand, an integrated combustor can produce heat forthe reaction in close proximity to the reaction zone, thus reducing heatlosses and increasing efficiency. Because traditional combustioncatalysts are not stable at high temperatures (above ˜1200° C.) due tonoble metal sintering, the integrated combustor must remove heat at arate sufficient to keep local temperatures at the catalyst surface belowthis level or risk rapid catalyst deactivation.

SUMMARY OF THE INVENTION

[0004] In an integrated reactor, combustion/heat generation should occurin close proximity to the endothermic reaction. Preferably, anexothermic reaction occurs in microchannels that are interleaved withmicrochannels in which there is an endothermic reaction. Co-flow ofendothermic and exothermic reaction streams is preferred; however,cross-flow or countercurrent flow are also options. The heat of anexothermic reaction is conducted from the exothermic reaction to theendothermic reaction catalyst, where it drives the endothermic reaction.

[0005] Preferably an exothermic reaction channel and/or endothermicreaction channel in the integrated reactors is a microchannel—that is, achannel having at least one dimension of 2 millimeter (mm) or less. Theuse of channels having a minimum dimension of more than 2 mm may be lesseffective since heat and mass transfer limitations may be magnified. Anintegrated combustor can use the high surface area of reactormicrochannels to remove heat as it is produced, thus keepingmicroreactor components from exceeding material temperature constraintswhile combusting with much less excess air (or diluent) than would benecessary for an external combustor.

[0006] In one aspect, the invention provides a method of conducting anendothermic reaction in an integrated combustion reaction, comprising:passing an endothermic reaction composition into at least oneendothermic reaction chamber, passing a fuel and an oxidant into atleast one exothermic reaction chamber wherein the fuel and oxidant eachhave a contact time in the combustion chamber of 50 ms or less, whereinthe exothermic reaction chamber comprises at least one exothermicreaction chamber wall that is adjacent at least one endothermic reactionchamber, wherein the endothermic reaction chamber comprises anendothermic reaction catalyst in contact with at least the at least oneendothermic reaction chamber wall that is adjacent at least oneexothermic reaction chamber, and transferring heat from the at least oneexothermic reaction chamber into the at least one endothermic reactionchamber at a rate of one or more of the following: at least 0.6 W/cc ofcombustion chamber volume, or at least 1 W/Cm² as based on the internalsurface area of the endothermic reaction chamber. The heat flux can bemeasured based on either a single exothermic reaction chamber ormultiple chambers in a multichamber device. So that, either case iswithin this aspect of the invention. In various preferred embodiments ofthe inventive methods and devices, the exothermic reaction chamber hasan internal dimension of less than 2 mm, more preferably less than 1.5mm, and in some embodiments, less than 1 mm; volumetric heat flux, basedon reaction chamber volume of greater than 10 W/cc, more preferablygreater than 100 W/cc, and still more preferably greater than 500 W/cc.Contact times in the exothermic and/or endothermic reaction chambers arepreferably less than 500 ms, more preferably 100 ms or less, still morepreferably 50 ms or less, more preferably 25 ms or less and still morepreferably 10 ms or less. Area heat flux (for the area of eitherreaction chamber is preferably 1 W/cm² or more, preferably 5 W/cm² ormore, more preferably 10 W/cm² or more, and still more preferably 20W/cm² or more.

[0007] In another aspect, the invention provides a method of steamreforming in an integrated combustion reactor, comprising: step a)passing steam and hydrocarbon into at least one endothermic reactionchamber wherein the steam to carbon ratio is less than 3:1 with apressure drop through the endothermic reaction chamber of less than 900psig (6000 kPa), step b) passing a fuel and an oxidant into at least oneexothermic reaction chamber wherein the fuel and oxidant each have acontact time in the combustion chamber of 100 ms or less, wherein theexothermic reaction chamber comprises at least one exothermic reactionchamber wall that is adjacent at least one endothermic reaction chamber,wherein the endothermic reaction chamber comprises an endothermicreaction catalyst in contact with at least the at least one endothermicreaction chamber wall that is adjacent at least one exothermic reactionchamber, step c) converting the steam and hydrocarbon to form CO and H₂such that the at least one endothermic reaction chamber has an outputdemonstrating a conversion of at least 50% of the hydrocarbon with aselectivity to CO of at least 50%; and simultaneously and continuouslyconducting steps a, b and c for at least 100 hours with less than a 2psi increase in pressure drop. Other preferred levels of steam to carbonratio are less than: 2.5:1; 2:1; and 1.5:1. In another embodiment, adevice is characterized by operation for 100 or 500 hours and then cutopen to reveal less than 0.1 gram of coke per each kilogram of methanefuel processed.

[0008] In another aspect, the invention provides a method of conductingsimultaneous exothermic and endothermic reactions in an integratedcombustion reactor, comprising: passing an endothermic reactioncomposition into at least one endothermic reaction chamber, passing afuel and an oxidant into at least one exothermic reaction chamberwherein the fuel and oxidant each have a contact time in the combustionchamber of 100 ms or less, wherein the oxidant is present in less than a50% excess needed to completely oxidize the fuel, and converting thefuel and air to products; and passing the products out of the integratedcombustion reactor, wherein less than 2500 ppm CO; wherein theexothermic reaction chamber comprises at least one exothermic reactionchamber wall that is adjacent at least one endothermic reaction chamber,wherein the endothermic reaction chamber comprises an endothermicreaction catalyst in contact with at least the at least one endothermicreaction chamber wall that is adjacent at least one exothermic reactionchamber. Alternatively to the low level of CO, or in addition to, wherethe oxidant is air, the products have less than 100 ppm NO_(x). Thelevel of excess oxidant is the total excess—in other words, this levelof conversion does not include any subsequent treatment steps in whichadditional oxidant is added in a treatment chamber (for example, acatalytic convertor). Other levels of NOx include: less than 100 ppm,less than 50 ppm, 20 ppm or less, 10 ppm or less and 5 ppm or less.

[0009] The invention further provides an integrated combustor,comprising: at least one exothermic reaction microchannel; wherein theexothermic reaction microchannel comprises at least one exothermicreaction microchannel wall that is adjacent at least one endothermicreaction microchannel, wherein the endothermic reaction microchannelcomprises an endothermic reaction catalyst in contact with at least theat least one endothermic reaction microchannel wall that is adjacent atleast one exothermic reaction microchannel; and further characterized byone or more of the preferred properties when tested using a Heat FluxMeasurement Test as described herein.

[0010] The invention also provides a layered integrated combustor,comprising: an outer exothermic reaction layer having a first volume; afirst combustor layer adjacent to the outer exothermic reaction layer,and disposed between the outer exothermic layer and an inner endothermicreaction layer; the inner endothermic reaction layer having a secondvolume and disposed between the first combustor layer and a secondcombustor layer; and the second combustor layer is disposed adjacent theinner endothermic reaction layer; wherein the first volume is 20 to 80%less than the second volume. More preferably, the first volume is 45 to55% less than the second volume. One nonlimiting example of this ICR isthe bonded ICR design described herein.

[0011] The invention further provides a method of conductingsimultaneous exothermic and endothermic reactions, comprising: flowing afuel into a combustion chamber; adding an oxidant to the combustionchamber such that the oxidant oxidizes the fuel and temperature in thecombustion chamber increases from the front of the combustion chamber tothe back; providing an endothermic reaction composition in anendothermic reaction chamber that is disposed adjacent to the combustionchamber, wherein the endothermic reaction chamber and the combustionchamber are separated by a thermally conductive wall; wherein theendothermic reaction composition endothermically reacts to formproducts. Where not otherwise specified, the front of the combustionchamber is defined as where the flow of fuel contacts a combustioncatalyst and an oxidant, and the back of the combustion chamber isdefined as the last part of the reaction chamber that contains acombustion catalyst and is in direct thermal contact (i.e., through awall) with an endothermic reaction chamber. In the bonded ICR designdescribed herein, the exhaust section is not in direct thermal contactwith the endothermic reaction chamber. Alternatively, the back of thecombustion chamber can be defined as where 95% of the thermal capacityof the fuel and oxidant has been expended.

[0012] The invention also provides a method of conducting an endothermicreaction, comprising: passing a fuel into a first fuel channel and,simultaneously, passing a fuel into a second fuel channel; adding anoxidant in a distributed fashion along the lengths of the first andsecond fuel channels; passing an endothermic reaction compositionthrough an endothermic reaction channel, said channel having a preheatsection connected to an endothermic reaction chamber that contains acatalyst; oxidizing the fuel in the first fuel channel to generate heatand form a first hot exhaust stream, and, simultaneously, oxidizing thefuel in the second fuel channel to generate heat and form a second hotexhaust stream; combining the first exhaust stream and the secondexhaust stream in one exhaust channel; transferring a portion of theheat generated in the first fuel channel through a wall and into theendothermic reaction chamber; transferring heat from the first exhauststream and the second exhaust stream through a wall of the exhaustchannel and into the first fuel channel; reacting the endothermicreaction composition in the endothermic reaction chamber to form heated,endothermic reaction products; flowing the heated endothermic reactionproducts into a product channel; transferring heat from the heatedendothermic reaction products in the product channel through a wall andinto the preheat section of the endothermic reaction channel.

[0013] The invention further provides an integrated combustion reactor,comprising: a combustion microchannel comprising a combustion catalyst;an endothermic reaction microchannel adjacent the combustionmicrochannel and comprising an endothermic reaction catalyst, theendothermic reaction catalyst having a length, in the direction of flow,of at least 10 cm; and a wall separating the combustion catalyst and theendothermic reaction catalyst. The long reaction catalyst leads tounexpected results of low contact time and high heat flux. The inventionalso includes methods of conducting endothermic reaction through thisICR, preferably with a low pressure drop. This aspect of the inventionis superior over shorter, channels with longer contact times because ofa reduced thermal gradient and increased device lifetime. In somepreferred embodiments, the endothermic reaction microchannel has aheight (the dimension perpendicular to flow and defining the shortestdistance from the center of the endothermic reaction microchannel to thecombustion microchannel) of 0.5 mm or less. In some preferredembodiments, a gap exists between a wall of the endothermic reactionmicrochannel and a surface of the endothermic reaction catalyst, and thegap is preferably 8 to 12 mil (0.2 to 0.3 mm).

[0014] In another aspect, the invention provides an ICR, comprising: astack of at least two microchannels wherein at least one of the at leasttwo microchannels comprises a removable catalyst insert and a catalystdoor. The invention also includes methods of salvaging or refurbishingan ICR by opening the catalyst door and removing catalyst.

[0015] In a further aspect, the invention provides an ICR, comprising:an exterior; an interior comprising at least two microchannels in astack and a catalyst precursor pathway that connects to at least one ofthe at least two microchannels and leads to the exterior; wherein thecatalyst precursor pathway is separate and distinct from process gasinlets and outlets. The invention also includes methods of adding acatalyst (or removing a catalyst by dissolving) through the catalystprecursor pathway.

[0016] In other aspects, the invention provides methods of starting upan ICR. One such method comprises: starting a combustion reaction byadding hydrogen into a fuel channel and subsequently reducing the flowof hydrogen into the fuel channel and increasing the flow of ahydrocarbon. The invention also includes start up methods in which anonreacting gas is passed through the endothermic process side toapproximate the flow rate during operation. Preferably the nonreactinggas is an inert gas such as nitrogen, but could be nonreacting processgas. The invention also includes start up methods in which the totalflow rate of fluids through the exothermic and/or endothermic reactionchambers remains substantially constant throughout start up. In anotherstart up method, a hydrocarbon fuel is subjected to a partial oxidationreaction prior to entering the combustion chamber, thus obtaining alower lightoff temperature.

[0017] In another aspect, the invention provides a method ofsimultaneously conducting an endothermic and an exothermic reaction inan ICR, comprising: passing an endothermic reaction mixture through anendothermic microchannel reaction chamber at two times or greaterpressure than the pressure in an adjacent exothermic microchannelreaction chamber.

[0018] In another aspect, the invention also provides a method ofsimultaneously conducting an endothermic and an exothermic reaction inan ICR, comprising: passing a mixture comprising H₂ and methane througha microchannel in an ICR; reacting the H₂ and methane with an oxidant toform water, CO₂ and CO and produce heat, thus removing H₂ and methanefrom the mixture; wherein a greater percentage of methane is removedfrom the mixture than the percentage of H₂ removed from the mixture, asmeasured by comparing the levels of H₂ and methane in the mixture beforepassing through the microchannel with the levels of H₂ and methane atany point after passing through the microchannel. This is an extremelysurprising result. The “removing” steps are by chemical reactions—notseparation techniques.

[0019] The invention further provides a method of forming a laminateddevice comprising forming a stack of shims that includes void-containingsacrificial shims; and applying heat and pressure to the stack anddeforming the sacrificial shims. The invention also provides a laminatedreactor comprising voids that, during operation, do not contain processstreams or heat transfer components.

[0020] In another aspect, the invention provides an integrated reactor,comprising: a first channel comprising an outlet; a second channelcomprising an outlet; a third channel connected to the outlets of thefirst and second channels; and a tongue projecting into the thirdchannel that, during operation, deflects flows from the outlets from thefirst and second channels and directs those flows in substantially thesame direction. Preferably, the integrated reactor is formed bylaminating shims.

[0021] In another aspect, the invention provides an integrated reactor,comprising: an endothermic reaction chamber that is connected through au-bend to a counterflow endothermic product channel; and an exothermicreaction chamber that is connected through a u-bend to a counterflowexhaust channel.

[0022] In a further aspect, the invention provides an integratedreactor, comprising: a fuel channel that is connected through a u-bendto a counterflow exhaust channel; and an oxidant channel nested betweenthe fuel channel and the exhaust channel.

[0023] In another aspect, the invention provides an integratedcombustion reactor, comprising a fuel channel and an adjacent oxidantchannel that are separated by a wall; wherein the wall comprises jetorifices. In one embodiment, the wall comprises non-circular jetorifices. In another embodiment, the wall has an uneven distribution ofjet orifices.

[0024] The invention also provides a laminated integrated reactor,comprising one exothermic reaction chamber comprising a reaction chamberwall and at least two exothermic reaction channels adjacent to thereaction chamber wall. For example, an exothermic reaction chamber canbe broken into two exothermic reaction microchannels by a support rib.

[0025] In yet another aspect, the invention provides an integratedcombustion system, comprising: a laminated integrated combustorcomprising a fuel inlet side and a combustion side; and at least twoconnections on the fuel inlet side; wherein the combustion side isrelatively free to expand with an increase in temperature, as comparedto the inlet side. The connections are typically connections for fluidinlets and outlets but may also include clamps or other means that wouldrestrict the expansion of the ICR. Typically, the two sides divide anICR into two sides of equal volume.

[0026] In a further aspect, the invention provides a laminated ICR,comprising: stacked sheets comprising a first sheet comprising a channelin the plane of the sheet and extending to a first opening at the edgeof the first sheet; a second sheet comprising a channel in the plane ofthe sheet and extending to a second opening at the edge of the secondsheet; wherein the edge of the first sheet and the edge of the secondsheet are on the same side of the laminated ICR; and a manifoldcomprising a conduit and an internal space that connects the first andsecond openings; wherein the conduit is selected from the groupconsisting of an exhaust conduit, a fuel conduit, an oxidant conduit, anendothermic reactant conduit, and an endothermic product conduit.

[0027] The invention further provides an integrated microchannelreactor, comprising: an exothermic reaction microchannel and anendothermic reaction microchannel adjacent to the exothermic reactionmicrochannel, (optionally) an oxidant channel, an exhaust channel and aproduct channel; and further, the integrated microchannel reactor isarranged in multiple layers with at least two exothermic reactionlayers, and at least two endothermic reaction layers. Additionally, thereactor is characterized by having multiple (more than 1) of each typeof channel and microchannel and includes 2 or more manifolds selectedfrom—one connecting at least two endothermic reaction microchannels, oneconnecting at least two exothermic reaction microchannels, oneconnecting at least 2 oxidant channels, one connecting at least twoexhaust channels, and one connecting at least 2 product channels;wherein at least two of these manifolds are connected at differentlengths along the integrated reactor.

[0028] In a further aspect, the invention provides a multizoneintegrated reactor, comprising: a manifold zone, a heat exchanger zone,and a reaction zone. Preferably, these zones are linearly arranged alongthe body of the integrated reactor. Preferably there is a transitionzone between the heat exchanger zone and the reaction zone where fluidstreams are split and recombined. In one preferred embodiment, thereactor includes a partial oxidation zone and a combustion zone.

[0029] The invention further provides an integrated reactor comprising acontiguous microchannel through a heat exchanger zone and a reactorzone.

[0030] In another aspect, the invention provides a method of conductingsimultaneous endothermic and combustion reactions in which a fuel ispartially oxidized prior to being combusted in a combustion chamber. Forexample, a hydrocarbon can be fully or partly converted to CO and the COburned in the combustion chamber. The invention also includes anintegrated reactor comprising a partial oxidation catalyst locatedupstream of a combustion catalyst, wherein the combustion catalyst islocated in a combustion chamber that is adjacent to an endothermicreaction chamber. The partial oxidation catalyst is preferably disposedwithin a fuel channel (or combustion channel) and can be in the form ofa flow through catalyst that occupies substantially all of across-section of the channel or a flow-by catalyst that leaves a bulkflow path through the channel.

[0031] In yet another aspect, the invention provides an endothermicreaction catalyst insert (preferably disposed in an integrated reactor)comprising a dense support (such as a metal foil) that is coated with acatalytically active metal. Preferably, the dense support includes aporous layer for increasing surface area of the active metal.

[0032] In another aspect, the invention provides a microchannel reactor,comprising: a first microchannel having a first length; an adjacent andoverlapping second microchannel having a second length defined by atleast one microchannel wall; wherein the second length is shorter thanthe first length; and a catalyst insert disposed in the secondmicrochannel. The at least one microchannel wall prevents the catalystinsert from sliding down the longer microchannel.

[0033] The invention also includes devices having any of the uniquestructural features or designs described herein. For example, theinvention includes a device having exothermic and/or endothermicreaction channels in a cross-flow relationship with the correspondingproduct channels.

[0034] The invention also includes processes using any of the devices,structural features designs or systems, or processes characterized byany of the properties or results described herein. In some preferredembodiments, the invention can be defined by a set of characteristicsthat could not be obtained from prior art devices or methods; variousaspects of the invention can be defined by characteristics including oneor more of the following: volumetric heat flux, area heat flux, pressuredrop through an exothermic or endothermic reaction channel, contacttime, levels of NO_(x), or CO in the combustion exhaust, thermalefficiency, low excess air, combustion conversion, approach toequilibrium of an endothermic reaction, conversion percent, productselectivity, thermal profile, fuel composition, steam to carbon ratio ina steam reforming reaction, level of coke formation, performance at agiven level of steam reforming pressure, pressure differential betweenthe endothermic and exothermic reaction channels, and performance as afunction of time. Levels of these and other characteristics can be foundin the Detailed Description and the Examples sections.

[0035] In preferred embodiments, aspects of the invention are combined;for example, in a preferred embodiment an inventive method ischaracterized by contact time and approach to equilibrium of anendothermic reaction.

[0036] Various embodiments of the present invention may possessadvantages such as: low pressure drop, low requirement for excess air,high combustion stability, short contact time for the endothermic and/orexothermic reactions, low CO and/or NOx formation, operation at nearstiochiometric air feed, greater safety, and high thermal cyclingdurability. Operation with a near stoichiometric air feed reduces theoverall load on the systems air blower or compressor which will lead tosignificant cost savings.

[0037] An additional advantage by reducing the combustion temperature(or temperature of the exothermic reaction) required to drive theendothermic reaction is use of alternate metals or metallurgy such thatlower cost materials or longer device life may be achieved.

[0038] Although the combustion may have both homogeneous andheterogeneous contributions, catalytic combustion in a microchannel (orchannel with a minimum open dimension less than or slightly greater thanthe quench diameter) will reduce the contribution of homogeneousreactions and favor heterogeneous (catalytic) combustion. This will alsofurther enhance safety by reducing gas phase reactions that mightotherwise take the combustion mixture well above the safe operatingtemperature limit of the material. Inhibition of gas phase combustiongrows stronger with decreasing channel minimum dimension and withincreasing catalytic surface area.

[0039] Glossary, Calculations and Testing Protocols

[0040] “Shims” refer to substantially planar plates or sheets that canhave any width and height and preferably have a thickness (the smallestdimension) of 2 millimeter (mm) or less, and in some preferredembodiments between 50 and 500 μm.

[0041] “Unit operation” means chemical reaction, vaporization,compression, chemical separation, distillation, condensation, heating,or cooling. “Unit operation” does not mean merely mixing or fluidtransport, although mixing and transport frequently occur along withunit operations.

[0042] A “microchannel” has at least one internal dimension of 2 mm orless.

[0043] An “open channel” is a gap of at least 0.05 mm that extends allthe way through a reaction chamber such that gases can flow through thereaction chamber with relatively low pressure drop.

[0044] “ICR” refers to an integrated combustion reactor that includes atleast one combustion channel adjacent to at least one endothermicreaction channel.

[0045] During operation, a reactant enters a combustion or reactionchamber in a bulk flow path flowing past and in contact with a “porousmaterial” or “porous catalyst.” A portion of the reactant molecularlytransversely diffuses into the porous catalyst and reacts to form aproduct or products, and then the product(s) diffuses transversely intothe bulk flow path and out of the reactor.

[0046] The term “bulk flow region” or “bulk flow path” refers to openareas or open channels within the reaction chamber. A reaction chamberwith a bulk flow path (or region) will contain a catalyst and there is agap between the catalyst surface and a reaction chamber wall or a secondcatalyst surface. A contiguous bulk flow region allows rapid gas flowthrough the reaction chamber without large pressure drops. In preferredembodiments there is laminar flow in the bulk flow region. Bulk flowregions within a reaction chamber preferably have a cross-sectional areaof 5×10⁻⁸ to 1×10⁻² m², more preferably 5×10⁻⁷ to 1×10⁻⁴ m². The bulkflow regions preferably comprise at least 5%, more preferably 30-80% ofeither 1) the internal volume of the reaction chamber, or 2) thecross-section of the reaction chamber.

[0047] “Equilibrium conversion” is defined in the classical manner,where the maximum attainable conversion is a function of the reactortemperature, pressure, and feed composition. For the case of hydrocarbonsteam reforming reactions, the equilibrium conversion increases withincreasing temperature and decreases with increasing pressure.

[0048] “Reaction chamber volume” is the internal volume of a reactionchamber (either exothermic or endothermic). This volume includes thevolume of the catalyst, the open flow volume (if present) and metalsupport ribs or fins (if present) within the reaction chamber volume.This volume does not include the reaction chamber walls. The reactionchamber volume must contain a catalyst somewhere within itscross-section and must be directly adjacent another reaction chamber forheat transport. For example, a reaction chamber that is comprised of a 2cm×2 cm×0.1 cm catalyst and a 2 cm×2 cm×0.2 cm open volume for flowimmediately adjacent to the catalyst, would have a total volume of 1.2cm³. If the same catalyst were divided into two sections or channelscomprising a catalyst volume of 1 cm×2 cm×0.1 cm (2 volumes of 0.2 cm³each) in each channel along with an open space immediately adjacent toeach catalyst of 1 cm×2 cm×0.2 cm (two volumes of 0.4 cm³ each) and ifthere were a metal rib or spacing between the two catalyst channels of0.1 cm×2 cm×0.3 cm (0.06 cm³), and if there was an adjacent reactionchamber of the opposite type (that is, an exothermic reaction chamberadjacent to an endothermic reaction chamber) then the total reactorvolume is defined as 1.26 cm³. This volume is used for calculations ofendothermic reaction chamber volumetric heat flux, area heat flux, andendothermic reaction contact time.

[0049] The “reactor core volume” is defined as the reaction chambervolume and all combustion chamber volume and the metal webs thatseparate the two chambers. The combustion chamber volume is defined asthe chamber volume in which the exothermic heat generating reactionoccurs and is adjacent to the reaction chamber volume. Perimeter metalis not included in reactor core volume.

[0050] As an example, a reactor that contains a reaction chamber volumeof 2 cm×2 cm×0.3 cm and a combustion chamber volume of 2 cm×2 cm×0.2 cmand a separating web of 2 cm×2 cm×0.1 cm would have a total reactor corevolume of 2.4 cm3.

[0051] The reactor core volume does not include any preheat exchangerzone volume that may or may not be attached to the reactor core volume.The preheat exchanger zone may be attached to the reactor but does notcontain an endothermic reaction catalyst along any plane that bisectsthe device orthogonal to the direction of flow.

[0052] “Endothermic reaction chamber heat flux” is defined as theendothermic reaction heat duty divided by the reaction chamber volume.

[0053] “Reactor core volume heat flux” is defined as the endothermicreaction heat duty divided by the reactor core volume.

[0054] “Heat exchanger flux” is defined as the total heat transferred tothe cold streams divided by the heat exchanger core volume.

[0055] “Heat exchanger core volume” is defined as the total heatexchanger volume inclusive of microchannels, ribs between microchannels,and the walls separating microchannels for all fluid streamstransferring heat. The heat exchanger volume is inclusive of the heatexchanger zone described in the text and accompanying figures. The heatexchanger core volume does not include the perimeter metal or manifoldsor headers. The heat exchanger core volume does not include theendothermic reaction chamber nor any volume that could be includedwithin any plane that bisects the endothermic reaction chamberorthogonal to the direction of flow.

[0056] “Average area heat flux” is defined as the endothermic reactionheat duty divided by the area of the endothermic reaction chamber heattransfer surface. The endothermic heat transfer surface is defined by aplanar area, which may be intermittent in the case of ribs or otherstructures in the endothermic reaction chamber, above which there isarea for flow of reactants and below which there is a wall thatseparates the endothermic reaction chamber and the exothermic reactionchamber. This area is the path for heat transfer from the exothermicreaction chamber to the endothermic reaction chamber.

[0057] “Web” is defined as the wall that separates the endothermicreaction chamber and the exothermic reaction chamber.

[0058] NO_(x), measurements are made of the exhaust stream while testinga selected device. The concentration of NO_(x), (in ppm) measured at 50%excess air, with combustion flows sufficient to maintain at least 850°C. combustion chamber temperature is called herein “the standard NO_(x),test measurement.” The measured value can be compared to NO_(x) levelsexceeding 100 ppm in conventional methane steam reformers.

[0059] The “apparent equilibrium conversion temperature” is the apparenttemperature based on methane conversion (or, more generally, hydrocarbonconversion) or the temperature required to produce an equilibriummethane conversion equal to the measured methane conversion at themeasured average process pressure. Average process pressure was assumedto be the average of the measured inlet and outlet pressures.Equilibrium gas compositions were calculated using the NASALEWISthermodynamic equilibrium code or ChemCAD. Methane conversion wascalculated from the dry product gas composition as measured by gaschromatograph according to the equation:${{CH}_{4}\quad {conversion}} = {1 - \frac{y_{{CH}_{4}}}{y_{{CH}_{4}} + y_{CO} + y_{{CO}_{2}}}}$

[0060] where y₁ is the mole fraction of component i.

[0061] Similarly, the apparent temperature based on selectivity to COwas estimated to be the temperature required to produce an equilibriumselectivity to CO value equal to the measured selectivity to CO at themeasured average process pressure.

[0062] The gaseous hourly space velocity (GHSV), is the inverse of thecontact time, multiplied by a conversion factor to convert millisecondsinto hours:${GHSV} = {\left( \frac{1}{CT} \right)\left( \frac{3600000\quad {ms}}{hr} \right)}$

[0063] where CT is the contact time in milliseconds. The rate ofvolumetric flow rate fed to the reactor is defined at the standardcondition of 0° C. and 1.013 bar for the purposes of calculating eithercontact time or GHSV. Thus the contact time and GHSV depend only on theinlet molar flowrate and the reaction chamber volume.

[0064] Heat Flux Measurement Test #1

[0065] Operate the device for a methane steam reforming reaction at 850C., an outlet pressure of no more than 1.70 bar (10 psig), 3:1steam-to-carbon ratio, and a contact time of 100 ms. Contact time isdefined as the total reaction chamber volume divided by the totalvolumetric inlet flowrate of reactants at standard temperature andpressure (STP: 273K and 1 atm absolute).

[0066] For example, if the reaction chamber volume is 1 cubiccentimeter, then the inlet total flowrate of reactants would be 0.6standard liters per minute for 100 ms contact time. The inlet flowrateof methane would be 0.15 standard liters per minute and the inletflowrate of steam would be calculated to be 0.45 liters per minute atstandard temperature and pressure. For this example, the inlet molarflowrate of methane would be roughly 0.00045 moles per second for the100 ms contact time. These numbers scale linearly with the totalreaction chamber volume. A 2 cubic centimeter reaction chamber volumewould require 0.0009 moles per second.

[0067] Methane conversion is determined by measuring the outlet productcomposition and the outlet flowrate of methane reforming reactionproducts and then calculating based on the following formula.

Conversion %=100×(moles methane in—moles methane out)/(moles methane in)

[0068] Moles methane in=inlet flowrate of methane at STP/(22.4 L/mol)

[0069] Moles methane out=[outlet flowrate of total product dry gas/(22.4L/mol)]×% methane in dry gas GC analysis

[0070] Dry gas is defined as the product gas stream flowrate aftercondensing the unreacted water or other condensable fluids.

[0071] Selectivity to CO %=100×(moles of CO/(moles of CO2+moles ofCO+moles of C(s) if present))

[0072] Selectivity to CO₂ %=100×(moles of CO2/(moles of CO2+moles ofCO+moles of C(s) if present))

[0073] Endothermic Heat load=(Conversion %/100)×Moles methane in×(Heatof reaction of steam reforming to carbon monoxide at 850 C. (226800J/mol)×selectivity to CO %+Heat of reaction of steam reforming ofmethane to carbon dioxide at 850 (193200 J/mol)×selectivity to CO₂%)/100, units of Watts

[0074] Endothermic Reaction Chamber Heat flux=Endothermic Heatload/endothermic reaction chamber volume, units of Watts/cm³

[0075] Reactor Core Volumetric Heat flux=Endothermic Heat load/reactorcore volume, units of Watts/Cm³

[0076] The following conditions must be met for the combustion reactionthat supplies heat for the heat flux measurement test:

[0077] 1. The gas phase fuel that must be used is hydrogen or methane.

[0078] 2. The air to fuel ratio is maintained at an excess airpercentage of 5 to 100%. The excess air is defined as the total molarflow rate of oxygen in the combination of fuel and air divided by themolar flow rate of oxygen needed to fully oxidize the fuel at its molarflow rate. For example, one mole of oxygen can fully oxidize two molesof hydrogen, so 100% excess air would correspond to a 4.76:1 molar ratioof air to hydrogen. Air is taken as 21% mole percent oxygen, balancenitrogen.

[0079] 3. The air and fuel flowrates and inlet temperature are adjustedto maintain the combustion reaction zone at 850° C. as measured byeither averaging the metal temperature over the last 25% of the reactionzone or as measured by the endothermic reaction product mixture givingan apparent equilibrium conversion temperature of 850° C. or higher.

[0080] Select conditions within the above-listed ranges to optimizeperformance. Calculate the endothermic reaction chamber heat flux bydividing the endothermic heat load by the reaction chamber volume.Calculate the reactor core volumetric heat flux.

[0081] Heat Flux Measurement Test #2

[0082] Operate the device for a methane steam reforming reaction at 850C., an outlet pressure of no more than 1.70 bar (10 psig), 3:1steam-to-carbon ratio, and a contact time of 20 ms. Contact time isdefined as the total reaction chamber volume divided by the totalvolumetric inlet flowrate of reactants at standard temperature andpressure (STP: 273K and 1 atm absolute).

[0083] Methane conversion is determined by measuring the outlet productcomposition and the outlet flowrate of methane reforming reactionproducts and then calculating based on the following formula.

Conversion %=100×(moles methane in—moles methane out)/(moles methane in)

[0084] Moles methane in=inlet flowrate of methane at STP/(22.4 L/mol)

[0085] Moles methane out=[outlet flowrate of total product dry gas/(22.4L/mol)]×% methane in dry gas GC analysis

[0086] Dry gas is defined as the product gas stream flowrate aftercondensing the unreacted water or other condensable fluids.

[0087] Selectivity to CO %=100×(moles of CO/(moles of CO2+moles ofCO+moles of C(s) if present))

[0088] Selectivity to CO₂ %=100×(moles of CO2/(moles of CO2+moles ofCO+moles of C(s) if present))

[0089] Endothermic Heat load=(Conversion %/100)×Moles methane in×(Heatof reaction of steam reforming to carbon monoxide at 850 C. (226800J/mol)×selectivity to CO %+Heat of reaction of steam reforming ofmethane to carbon dioxide at 850 (193200 J/mol)×selectivity to CO₂%)/100, units of Watts

[0090] Endothermic Reaction Chamber Heat flux=Endothermic Heatload/endothermic reaction chamber volume, units of Watts/cm³

[0091] Reactor Core Volumetric Heat flux=Endothermic Heat load/reactorcore volume, units of Watts/cm³

[0092] The following conditions must be met for the combustion reactionthat supplies heat for the heat flux measurement test:

[0093] 1. The gas phase fuel that must be used is hydrogen or methane.

[0094] 2. The air to fuel ratio is maintained at an excess airpercentage of 50%. The excess air is defined as the total molar flowrate of oxygen in the combination of fuel and air divided by the molarflow rate of oxygen needed to fully oxidize the fuel at its molar flowrate. For example, one mole of oxygen can fully oxidize two moles ofhydrogen, so 100% excess air would correspond to a 4.76:1 molar ratio ofair to hydrogen. Air is taken as 21% mole percent oxygen, balancenitrogen.

[0095] 3. The air and fuel flowrates and inlet temperature are adjustedto maintain the combustion reaction zone at 850° C. or higher asmeasured by either averaging the metal temperature over the last 25% ofthe reaction zone or as measured by the endothermic reaction productmixture giving an apparent equilibrium conversion temperature of 850° C.or higher.

[0096] Select conditions within the above-listed ranges to optimizeperformance. Calculate the endothermic reaction chamber heat flux bydividing the heat load by the reaction chamber volume. Calculate thereactor core volumetric heat flux.

[0097] Heat Flux Measurement Test #3

[0098] Operate the device for a methane steam reforming reaction at 850C., an outlet pressure of no more than 1.70 bar (10 psig), 3:1steam-to-carbon ratio, and a contact time of 25 ms. Contact time isdefined as the total reaction chamber volume divided by the totalvolumetric inlet flowrate of reactants at standard temperature andpressure (STP: 273K and 1 atm absolute).

[0099] Methane conversion is determined by measuring the outlet productcomposition and the outlet flowrate of methane reforming reactionproducts and then calculating based on the following formula.

Conversion %=100×(moles methane in—moles methane out)/(moles methane in)

[0100] Moles methane in=inlet flowrate of methane at STP/(22.4 L/mol)

[0101] Moles methane out=[outlet flowrate of total product dry gas/(22.4L/mol)]×% methane in dry gas GC analysis

[0102] Dry gas is defined as the product gas stream flowrate aftercondensing the unreacted water or other condensable fluids.

[0103] Selectivity to CO %=100×(moles of CO/(moles of CO2+moles ofCO+moles of C(s) if present))

[0104] Selectivity to CO₂ %=100×(moles of CO2/(moles of CO2+moles ofCO+moles of C(s) if present))

[0105] Endothermic Heat load=(Conversion %/100)×Moles methane in×(Heatof reaction of steam reforming to carbon monoxide at 850 C. (226800J/mol)×selectivity to CO %+Heat of reaction of steam reforming ofmethane to carbon dioxide at 850 (193200 J/mol)×selectivity to CO₂%)/100, units of Watts

[0106] Endothermic Reaction Chamber Heat flux=Endothermic Heatload/endothermic reaction chamber volume, units of Watts/cm³

[0107] Reactor Core Volumetric Heat flux=Endothermic Heat load/reactorcore volume, units of Watts/cm³

[0108] The following conditions must be met for the combustion reactionthat supplies heat for the heat flux measurement test:

[0109] 1. The gas phase fuel that must be used is hydrogen or methane.

[0110] 2. The air to fuel ratio is maintained at an excess airpercentage of 5 to 100%. The excess air is defined as the total molarflow rate of oxygen in the combination of fuel and air divided by themolar flow rate of oxygen needed to fully oxidize the fuel at its molarflow rate. For example, one mole of oxygen can fully oxidize two molesof hydrogen, so 100% excess air would correspond to a 4.76:1 molar ratioof air to hydrogen. Air is taken as 21% mole percent oxygen, balancenitrogen.

[0111] 3. The air and fuel flowrates and inlet temperature are adjustedto maintain the combustion reaction zone at 850° C. or higher asmeasured by either averaging the metal temperature over the last 25% ofthe reaction zone or as measured by the endothermic reaction productmixture giving an apparent equilibrium conversion temperature of 850° C.or higher.

[0112] Select conditions within the above-listed ranges to optimizeperformance. Calculate the reactor core volume heat flux by dividing theheat load by the reactor core volume. Calculate the reactor corevolumetric heat flux.

[0113] Pressure Test—High Temperature Test for ICR

[0114] In preferred embodiments, any of the devices described herein arecapable of withstanding internal pressure differences. For example, somepreferred embodiments meet the requirements of the following pressuretest. For a microchannel unit operation device with at least onecritical channel dimension less than about 2 mm, operate with at leasttwo inlet fluid streams. The first fluid stream must be at 850 C. and180 psig. The second fluid stream must be at 800 C. and 10 psig. Anyflow rate may be used, or alternatively, stagnant flow may be used withthe ends of the two fluid streams exiting the device temporarily sealed.Operate the device with these pressures and temperatures for 300 hours.After 300 hours operation, pressurize each fluid flow line to 50 psigand hold for 2 hours. The pressure must remain constant indicatingminimal leak paths to the environment. Then, pressurize the second fluidflow line to 50 psig, leaving the first fluid flow line open toatmosphere, and hold for 2 hours. The pressure must remain constantindicating minimal internal leak paths. A minimal leak path is definedas a leak rate of less than 10⁻⁶ standard cubic centimeters per secondof helium when helium is used as the fluid for the final leak test.

BRIEF DESCRIPTION OF THE FIGURES

[0115]FIG. 1 schematically illustrates a cross-sectional view of areactor of the present invention.

[0116] FIGS. 2-4 are schematic illustrations of various designs forfluid flow in an ICR.

[0117]FIG. 5 illustrates channel deformation resulting from pressbonding.

[0118]FIG. 6 illustrates sacrificial channels to protect internalchannels from deformation during hot isostatic press bonding.

[0119]FIG. 7 is a list of ordered shims for assembling an ICR devicewith a two-stream loop.

[0120] FIGS. 8-21 are illustrations of shim designs for a two-streamloop bonded ICR device.

[0121] FIGS. 22A-22C are illustrations of shim designs for a welded ICRdevice. Testing results from ICRs having this design are reported in theExamples section (Devices N2, N3, M1, and M2).

[0122]FIG. 23 is a schematic illustration of a tongue that can redirectflows in a two-stream loop.

[0123] FIGS. 24A-24C illustrate tooling for inserting a catalyst insertinto a bonded reactor.

[0124] FIGS. 25-42 are data graphs that correspond to the Examples.

DETAILED DESCRIPTION OF THE INVENTION

[0125] An integrated reactor according to the present invention includesan exothermic reaction chamber and an adjacent second reaction chamberthat contains a catalyst capable of catalyzing an endothermic reaction.A reaction chamber wall separates the exothermic and endothermicreaction chambers.

[0126] A cross-sectional view of one embodiment of an exothermicreaction channel and endothermic reaction channel is illustrated inFIG. 1. The exothermic (e.g., combustion) channel and/or endothermic(e.g., reforming) channel can contain a catalyst insert 204 with spacers206. The spacers 206 press the catalyst insert against reaction chamberwall 210. In this illustration, flow in either channel is into or out ofthe page. Wall 210 separates catalyst insert 204 from reaction chamber214. Preferably, the catalyst insert 204 contacts channel surface 211,and for enhanced thermal conduction also contacts internal wall surfaces213 and 215. Preferably the spacers 206 are adjacent to (and preferablycontact) the reaction chamber wall surfaces 213 and 215. The spacerscould be integral to the catalyst insert that is pre-formed in a singlepiece, or separate items placed on the catalyst insert.

[0127] In the present invention, the exothermic (and/or endothermic)reaction chamber(s) preferably has a height (a dimension that isperpendicular to flow, and, in laminated devices, the stackingdirection) of 2 mm or less, more preferably 1 mm or less, and in someembodiments 0.5 mm or less, and in some embodiments in the range of 0.1to 1 mm. The dimensions of a reaction chamber are the internaldimensions and include catalyst but do not include chamber walls. Areaction chamber wall (separating the exothermic and endothermicreaction chambers) should be thermally conductive and preferably has aheight (the distance between reaction chambers) of 5 mm or less, morepreferably 2 mm or less, and in some embodiments a height of 1 to 2 mm.A short heat transport distance is desired for good performance. It hasbeen discovered that these short heat transport distances, combined withpreferred reactor configurations, can provide surprisingly highvolumetric productivity and low pressure drop.

[0128] A reaction chamber has dimensions of height, width and length.The height and/or width is preferably about 2 mm or less, and morepreferably 1 mm or less. The length of the reaction chamber is typicallylonger. Preferably, the length of the reaction chamber is greater than 1cm, more preferably in the range of 1 to 50 cm. Surprisingly, it hasbeen discovered that superior results can be obtained in an integratedreactor having a reaction channel length of at least 10 cm, morepreferably at least 17 cm, and in some embodiments in the range of 10 cmto 50 cm. Preferably, the adjacent endothermic and exothermic reactionchannels have substantially the same length to match the heat generationload with the heat consumption in the endothermic reaction.

[0129] Typically, the sides of a reaction chamber are defined byreaction chamber walls. These walls are preferably made of a hardmaterial such as a ceramic, an iron based alloy such as steel, or monel,or high temperature nickel based superalloys such as Inconel 625,Inconel 617 or Haynes 230. Preferably, the reaction chamber walls arecomprised of a material which is durable and has good thermalconductivity.

[0130] Preferably an exothermic reaction chamber contains a bulk flowpath. In some preferred embodiments, an exothermic and/or endothermicreaction chamber has an inlet and an outlet with a contiguous bulk flowpath from the inlet to the outlet. Preferably, the height of the bulkflow path (open channel gap) within a reaction chamber is less than orequal to 1 mm and the length (direction of net flow) is preferably lessthan or equal to 20 inches (50 cm). The width of a catalyst within abulk flow path may vary but is preferably at least 20% and morepreferably 50% of the circumference of the bulk flow path. In thesepreferred embodiments, the pressure drop from inlet to outlet ispreferably less than 20%, more preferably less than 10% of system inletpressure. The pressure drop is preferably less than 350 kPa, morepreferably the pressure drop is less than 200 kPA and still morepreferably the pressure drop is less than 70 kPa. A low pressure drop isdesired to reduce the size and cost of other system equipment such aspumps and compressors. In other less preferred embodiments, the reactionchamber may include a section, such as a porous plug, that interfereswith bulk flow.

[0131] The integrated combustion reactor preferably utilizes designsthat 1) prevent combustion reaction upstream of the endothermicmicrochannel catalyst, and 2) distribute one of the combustion reactantsacross the microchannel cross-section, which may include uniformdistribution, distribution with disproportional loading at the front(the upstream section) of a reaction chamber, and distribution withdisproportional loading at the back of a reaction chamber. An especiallypreferred method of distributed flow is the use of jets from which apressurized oxidant shoots into a fuel channel—most preferably, thisoxidant flows onto a combustion catalyst that is disposed on a reactionchamber wall that is directly adjacent to an endothermic reactionchamber. The absolute pressure of the oxidant need only be slightlylarger than the absolute pressure of the fuel stream, from a tenth of apsi to ten psi or more.

[0132] Reactors can be designed to simultaneously conduct one exothermicreaction and one endothermic reaction. Alternatively, a single devicecan be designed to simultaneously conduct numerous exothermic and/orendothermic reactions. For example, two or more different exothermic(and/or endothermic) reactions could be conducted on separate layerswithin a single device. Alternatively, multiple reactions can beconducted within the same layer of a device. For example, a singlechannel can have a partial oxidation reaction chamber followed by acombustion chamber. Such a construction could be especially useful, forexample, to partially oxidize methane or other hydrocarbon in a fuelcomposition and flowing the partially oxidized fuel into the combustionchamber. Alternatively, a hydrocarbon mixture could be partly or fullypre-reformed to methane prior to being reformed to hydrogen in anendothermic reaction chamber.

[0133] In some preferred embodiments, the inventive reactors containpreheat zones for the fuel, oxidant and/or endothermic reactants. Insome preferred embodiments, the preheat zones are or include upstreamportions of the same microchannels through which a composition travelsto the exothermic or endothermic reaction chambers. In especiallypreferred embodiments, this can be accomplished by flowing heatedproducts through a u-bend and then back down through a channel that isadjacent the upstream portion of the microchannel containing thereaction chamber (see the Examples).

[0134] In some preferred embodiments, the exhaust from the combustionchamber is used to preheat fuel and/or endothermic reactants. In somepreferred embodiments, a microchannel exhaust chamber is located withinthe integrated combustion reactor and downstream of the combustionchamber. Preferably, the exhaust chamber contains a combustion catalystbecause additional heat can be generated and because pollutants can bereduced. In some preferred embodiments involving steam reforming, theendothermic reaction chamber contains a steam reforming catalyst whilethe portion of the flow path downstream of the reforming catalyst doesnot have a catalyst—this improves yield since the reaction is inhibitedfrom re-equilibrating as it cools. Even without a catalyst in theprocess product return channel, the reactor walls may have some inherentcatalytic function and partially re-equilibrate the products. For steamreforming of a hydrocarbon, this may be advantageous if the desiredproduct is hydrogen, as the water gas shift reaction is enhanced atcooler temperatures. If synthesis gas is desired, it is advantageous toinhibit re-equilibration of the product stream.

[0135] In view of the need to conduct multiple operations on a fluidstream in an integrated reactor, in some preferred embodiments, theintegrated reactors include a substantially continuous microchannel(i.e., one that has microchannel dimensions substantially throughout itslength) or microchannels that have a length of at least 1 cm, morepreferably at least 10 cm, and in some embodiments 1 to 200 cm.

[0136] In some embodiments, reaction chambers have the shape ofparallelepipeds; however, it should be appreciated that other shapessuch as cylinders (for example, adjacent cylinders or cylinders with anexothermic catalyst partly surrounded by an arc containing anendothermic reaction catalyst, or vice versa), or prisms (preferablyclose packed prisms to reduce heat transport distance and maximizesurface area for thermal transport). Such shapes could be made, forexample, by drilling through a block or laminating a stack of shims withshapes, aligned apertures such that the stacked and bonded shims form apassage having borders defined by the edges of the apertures. Toincrease surface area, in some embodiments, the reaction chamber (eitherexothermic, endothermic, or both) can have a projections or a set ofmicrochannels. In some preferred embodiments, a reaction chamber wallhas fins. The fins can have any shape and can extend partly orcompletely over the width of a reaction chamber. Preferably, a catalystor catalysts are deposited over the reaction chamber walls to formexothermic or endothermic reaction chambers.

[0137] In addition to thermal transfer between adjacent reactionchambers, in some embodiments, a reaction chamber can be in thermalcontact with a microchannel heat exchanger. This combination of reactionchamber(s) and heat exchanger(s) can result in high rates of thermaltransfer. Examples and more detailed description including the use ofmicrochannel heat exchangers are provided in U.S. patent applicationSer. No. 09/492,246, filed Jan. 27, 2000, incorporated herein byreference. In some embodiments, the reaction chamber(s) and heatexchangers have a heat flux of at least 0.6 W per cubic centimeter ofreactor volume.

[0138] Adjacent layers of exothermic and endothermic reaction chambersis a general feature of the invention, and in some preferred embodimentsthere are at least 2, more preferably at least 5 layers of endothermicreaction chambers alternating with at least 1, more preferably at least4 layers of exothermic reaction chambers. Preferably, the apparatus isdesigned, and the methods performed such that outer layers have less(most preferably, one half) the mass flow of reactants as compared withinner layers of the same type; for example, in a device having 2exothermic reaction layers interleaved between 3 endothermic reactionlayers, the outer 2 endothermic reaction layers preferably have one halfthe flow of the inner endothermic reaction layer. In the bonded ICRdevice described below, each two-stream loop (having an “M”configuration) is a layer; but the layers on the top and bottom of theshim stack are half two-stream loops that, during operation, containonly half the mass flow of the internal layers (which are fulltwo-stream loops). The feature of two streams entering from the bottomof a device, flowing up through manifold, exchanger, and reaction zones,and then merging near the U-bend before returning as a conjoined flowback through the zones is referred to as a two-stream loop.

[0139] The devices may be made of materials such as plastic, metal,ceramic and composites, depending on the desired characteristics. Wallsseparating the device from the environment may be thermally insulating;however, the walls separating adjacent exothermic and endothermicreaction chambers should be thermally conductive.

[0140] There are numerous possible configurations for the ICR reactorsystem of the present invention. In a preferred embodiment, a singleintegrated device contains a reactor zone, a preheat or recuperativeheating zone, and a manifold zone. More preferably, this device ischaracterized by a free-end to allow for thermal expansion and stressminimization at the hottest end of the device. To create a free-end, thereactant stream makes a U-bend to form the product stream. Thecombustion stream (combined fuel and air) also makes a U-bend to formthe combustion exhaust stream. The “free end” is characterized by havinga greater degree of freedom than the non-free end; this is accomplishedby having relatively few or, more preferably, no connections for fluidinlets and outlets; instead, the fluid inlet and outlets areconcentrated on the non-free end of the reactor that is subjected toless thermal stress. During operation, the free end of the reactor istypically hotter than the non-free end of the device. The free end ofthe reactor should be relatively free of clamps or other components thatwould inhibit thermal expansion.

[0141] In some preferred embodiments, the flow orientations arecharacterized by a two-stream loop geometry (see schematic in FIG. 2). Areaction layer contains a reactant channel that flows through a manifoldzone, through a pre-heat zone, and then into the reaction zone (reactionchamber volume) within the same reaction microchannel. This processreaction stream then makes a U-turn into a product return stream thatflows countercurrent to the originating reaction channel. Preferably, atall times during the flow path, the fluids are contained within achannel that has at least one dimension in the microchannel range. Onthe other side of the product return channel, a second reactant channelflows in a counter-current manner. Near the top of the U-bend, the twoprocess reaction channels preferably join to form the common productreturn channel down the center. As the two process reaction streamsmerge into a single product return stream, preferably there is aninterspaced tongue to prevent direct flow impingement and reduce flowinstabilities.

[0142] Adjacent to the process layer, is a combustion layer. Theoutermost channels of the combustion layer are comprised of a fuelchannel. Fuel flows through a manifold zone at the bottom of device,then through the preheat or recuperative heat exchanger zone in acontiguous microchannel, and then into a combustion reaction zone(combustion chamber volume). Preferably, air (or other oxidant) flows inan oxidant channel that is adjacent to each of the fuel channels throughthe manifold and exchanger zones. Air is then bled into the combustionchamber or zone through the use of jet orifices to meter air along thelength of the combustion zone. The oxidant channel stops before theU-bend section. The two fuel channels are joined near the end of thereaction zone. The two streams are preferably merged into a singleexhaust channel that flows down the innermost channel of the combustionlayer. As the two combustion streams merge into a single exhaust returnstream, preferably there is an interspaced tongue to prevent direct flowimpingement and reduce flow instabilities.

[0143] The process reaction and combustion layers may be repeatedmultiple times to achieve the desired capacity. The terminating layer ofthe repeating unit is characterized by a single process reactionchannel, adjacent to the combustion layer, which makes a U-bend into aproduct return channel that comprises flow from a single reactantchannel. Alternatively, the outermost layer could be comprised of acombustion layer rather than a reactant layer.

[0144] The recuperative heat exchanger zone is comprised of 5 fluidsthat exchange heat. The repeating channels are as follows: product,reactant, fuel, air, exhaust, air, fuel, reactant, product, reactant,fuel, and so on. Heat from the product and the combustion exhauststreams preheat the reactant, combustion fuel, and combustion airstreams.

[0145] The five streams are preferably manifolded at the cooler end ofthe device to enhance the device mechanical life. In a particularlypreferred embodiment, one fluid is manifolded directly out the bottom ofthe device. The other four streams can be divided two per side. Each ofthe five manifold areas are connected to external pipes to bring in orremove fluids from the device.

[0146] In one alternative design, see schematic in FIG. 3, the floworientation is characterized by a single reaction and combustion channelthat make a U-turn and return to the manifolding zone. In this design,referred to as a “single-stream loop,” the flowpaths are as follows.Reactant flows through a manifold zone, through a pre-heat zone, andthen into the reaction zone within the same reaction microchannel. Thisprocess reaction stream then makes a U-turn into a product return streamthat flows countercurrent to the originating reaction channel. Thisproduct return stream may also contain catalyst and as such may supportfurther reaction. After flowing through the reaction zone, the productchannel enters the heat exchange zone before flowing out the manifoldingzone. Adjacent to this process reaction layer is a combustion layer.Parallel to the reactant channel, but separated by a metal web, is thefuel channel. Fuel flows through a manifold zone at the bottom ofdevice, then through a preheat or recuperative heat exchanger zone in acontiguous microchannel, and then into a combustion reaction zone. Airflows adjacent to the fuel channel through the manifold and exchangerzone. In preferred embodiments, air (or other oxidant) is fed into thecombustion zone through the use of jet orifices to meter air along thelength of the combustion zone. The air channel stops before the U-bendsection. The fuel channel then makes its U-turn overtop of the airchannel to connect with the exhaust return channel. The exhaust channelmay still contain catalyst and promote further combustion. The airchannel, which is internal to the combustion U—fuel to exhaust, cancontain a second set of apertures on the opposite wall to the first setto meter air into the downstream combustion channel as desired.Combustion on the return pass after the U-bend provides heat to theendothermic reaction that occurs on the adjacent wall. The correspondingendothermic reaction channel can be on the return path of theendothermic process channel after the U-bend. The reactant andcombustion U-bend layers are repeated as often as required to providesufficient capacity for the device. The terminating layer of therepeating unit on one end of the device is characterized by a singleprocess reaction channel, adjacent to the combustion zone, which makes aU-bend into a product return channel that comprises flow from a singlereactant channel. The outer end will require a lower capacity reactantchannel and no catalyst in the product return channel corresponding tono combustion heat at the outermost edge of the device. Alternatively,the outermost layer could be designed to include a combustion layer withcombustion only occurring on the first pass in the combustion zone.

[0147] The recuperative heat exchanger zone is comprised of 5 fluidsthat exchange heat. The repeating channels are as follows: product,reactant, fuel, air, exhaust, product, reactant, fuel, and so on. Heatfrom the product and the combustion exhaust stream, preheat thereactant, combustion fuel, and combustion air.

[0148] The five streams are manifolded at the cold end of the device.One fluid is manifolded directly out the bottom of the device. The otherfour streams are divided two per side. Each of the five manifold areasare connected to external pipes to bring or remove fluids to or from thedevice. This is in an analogous manner as to the previous embodiment.

[0149] In another alternative embodiment of the device, see theschematic diagram in FIG. 4, the flow orientation is a single-streamloop geometry to create a free end for the device. In this embodiment,additional internal microchannel features are added in the zone betweenthe reaction zone and heat exchange zone. This region, which will betermed a transition zone, accomplishes a rearrangement of the streams sothat they have different orientations between the reactor and heatexchange zones. The transition zone may also act to split or mergestreams to create more or fewer fluid channels in the exchanger zone.The flowpaths are as follows. Reactant flows through a manifold zone,through a pre-heat zone, and then into the reaction zone within the samereaction microchannel. This process reaction stream then makes a U-turninto a product return stream that flows countercurrent to theoriginating reaction channel. This product return stream may alsocontain catalyst. After progressing out of the reaction zone, theproduct channel undergoes heat exchange and then the product fluidenters the manifolding zone to make its way to the outlets of thedevice. Adjacent to this process reaction U layer, is a combustionlayer. Parallel to the reactant channel, but separated by a metal web isthe fuel channel. Fuel flows through a manifold zone at the bottom ofdevice, then through the preheat or recuperative heat exchanger zone ina contiguous microchannel, and then into a combustion reaction zone. Air(or other oxidant) flows adjacent to the fuel channel through themanifold and exchanger zone. Air is then fed into the combustion zonethrough the use of jet orifices to meter air along the length of thecombustion zone. In this embodiment, the air channel also performs aU-bend, with the air U occurring entirely within the combustion U. Thefuel channel makes its U-turn overtop of the air U to connect with theexhaust return. The exhaust channel contains catalyst which promotesfurther combustion. The air channel downstream U contains the smallapertures which are used to meter air into the downstream combustion Uas desired. The air channel dead ends, and does not return into the heatexchanger zone. The process reaction and combustion layers may berepeated multiple times to achieve the desired capacity. As they arerepeated, fresh reactant in an upstream reaction channel can be matchedwith and is separated by a wall from the upstream combustion channelwhere fuel and air mix. Likewise, downstream combustion is matched withdownstream reaction. The terminating layer of the repeating unit on oneend of the device is characterized by a single process reaction channel,adjacent to the combustion zone, which makes a U-bend into a productreturn channel that comprises flow from a single reactant channel. Ifdownstream reactions are being employed, then the opposite end willfeature a lower capacity downstream product channel fed by acorresponding lower capacity reactant channel which does not have anycatalyst and does not undergo reaction at the outermost channel.Alternatively, the outermost layer could be a combustion layer.

[0150] The recuperative heat exchanger zone is comprised of 5 fluidsthat exchange heat. These fluids are actually contained in 7 differentflowpaths, where air is joined from two fluid channels in the heatexchanger zone into one channel entering the reaction zone. The exhaustchannel is split into two channels as it heads into the heat exchangerzone. The repeating channels in the heat exchange zone are as follows:product, reactant, fuel, exhaust, air, exhaust, air, product, reactant,fuel, and so on. Heat from the product and the combustion exhauststreams, preheat the reactant, combustion fuel, and combustion airstreams.

[0151] In order to achieve this orientation, the air stream and exhauststream must split and interleave within the transition zone. This isaccomplished by taking advantage of the three dimensional nature of themicrochannels, allowing the two flows to bypass one another as theysplit and exchange locations. This also takes advantage of the spacebelow the air channel's dead end within the reaction zone. Splitting andjoining air and exhaust streams allows for the microchannel exchanger inthe exchanger zone to operate much more effectively, as channels withsmaller hydraulic diameters are created that enhance heat transferrates.

[0152] The five fluids are manifolded at the cold end of the device. Onefluid is manifolded directly out the bottom of the device. The otherfour streams are divided two per side. Each of the five manifold areasis connected to external pipes to bring or remove fluids to or from thedevice. This is in an analogous manner to the previous embodiments.

[0153] It is recognized that the embodiments of the ICR design could beachieved by alternate shim design styles, including slicing the shims inany of the three planes that comprise a device.

[0154] In some preferred embodiments, the combustion zone is enhanced byoperating with a partial oxidation (“POx or POX”) catalyst preceding thecombustion catalyst to convert the hydrocarbon fuel to mostly hydrogenand carbon monoxide. The synthesis gas fuel in the combustion zone is aneasier fuel to combust than some hydrocarbons such as methane. The POxcatalyst may be in the form of a flow through structure such as a foam,wad, pellet or powder, or gauze. The POX catalyst may be in the form ofa flow by structure such as a felt with a gap adjacent, a foam with agap adjacent, a fin structure with gaps, a washcoat, or a gauze that isparallel to the flow direction with a corresponding gap for flow. ThePOX catalyst may be directly washcoated on the walls of the POx zone.The wall gap may be made thinner than the combustion zone to enhancemass transfer to the catalyst coating on the wall.

[0155] The POX-assisted combustion can be incorporated into either thetwo-stream loop concept or the single-stream loop concepts. POX-assistedcombustion in a microchannel may also be further extended to otherdesigns and design concepts, or wherever one may desire to combust ahydrocarbon fuel in a microchannel either with or without a concurrentendothermic reaction.

[0156] The POx catalyst could be inserted in the device prior toassembly and bonding. The POX catalyst could be washcoated prior tobonding using the same access holes used for the combustion washcoatcatalyst. The POx catalyst could be inserted in the device through thecold-end, if the fuel channel is selected as the stream that enters thebottom of the device and thus allowing a straight channel for catalystinsertion.

[0157] An additional advantage of the POx assisted combustion is theease of device startup. Many hydrocarbons require elevated temperatureto initiate combustion, whereas the POx reaction can be partiallyinitiated at much lower temperatures. As an example, for methane the POxlight off temperature is less than 400 C., where as a temperatureexceeding 800 C. is required for direct methane combustion.

[0158] The use of POx assisted combustion allows for fuel flexibilitywith an integrated combustion reactor. The optimal jet spacing often isdependent upon the nature of the fuel combustion. POx assistedcombustion will allow one device to operate efficiently with multiplecombustion fuels and multiple endothermic reaction hydrocarbons—if thesame catalyst is effective for multiple endothermic reactions such ashydrocarbon reforming.

[0159] For the POx-assisted combustion, a mixture of fuel and air flowsalong the fuel chamber through the exchanger zone, and then through thePOx zone before entering the combustion zone. The air required for thePOx reaction could be mixed inside the microchannel device to enhancesafety of the process. For methane, a typical fuel to oxygen ratio inthe POx zone is 2:1. More oxygen may be added to keep the mixture out ofa coking regime. The mixture could drop as low as 1.5:1.

[0160] Alternatively, air could be mixed into the fuel stream prior toor during the POX zone via the use of jets to control the airdistribution.

[0161] The use of POx assisted combustion may be used in any of thepresented design configurations for the ICR, or alternatively it couldbe used in modified or alternative design configuration.

[0162] Thus, the invention also includes combustion methods in which thehydrocarbon/CO mass ratio in a fuel decreases before the fuel iscombusted in a combustion chamber. In some preferred embodiments, thehydrocarbon/CO mass ratio decreases by at least 20%, more preferably atleast 50%, and in some embodiments essentially all of the hydrocarbon iseliminated.

[0163] Tongue Description

[0164] In the present invention, it is preferred to force the streams toflow in the same direction prior to combining the flows of two streams.Preferably this is accomplished by use of a tongue 232 as shown in FIG.23. In the illustrated embodiment, two parallel combustion streams 234and 236 flow through u-bends 238, 231, against tongue 232 and intocombined flow path 237. Combination of the streams in this mannerresolves the momentum impulse forces into the same direction and permitsthe two streams to combine independently of the value of the individualflow rates. Thus, intermittent flow is minimized.

[0165] Recirculation eddies will exist in the comers as well as thebottom of the u-bend. The size of these recirculation zones can beminimized by adjusting the gap sizes 230, 235 and 239. The size of theu-bend inlet 235 should be similar to the size of the u-bend outlet 230.Preferably the cross-sectional area (height×depth) ratio of 235/230 isin the range of 0.1 to 10, more preferably 0.6 to 1.8, and still morepreferably in the range of 0.8 to 1.3, preferably the u-bend inlet,u-bend and u-bend outlet are coplanar and the same depth (relative toFIG. 23, depth is perpendicular to the paper). Preferably, the combinedflow channel 239 is similar in size to the combination of the inletchannels 235 and 236. Preferably the cross-sectional area (height×depth)ratio of (235±236)/239 is in the range of 0.1. to 10, more preferably0.5 to 2.0, and still more preferably in the range of 0.8 to 1.3,preferably the u-bend inlet, u-bend and u-bend outlet are coplanar andthe same depth (relative to FIG. 23, depth is perpendicular to thepaper). The height, h, of the u-bend inlet 235 is preferably in therange of 0.01 mm to 10 mm, more preferably 0.02 mm to 1.5 mm, and stillmore preferably in the range of 0.1 mm to 0.7 mm. The height, h, of theu-bend outlet 239 is preferably in the range of 0.02 mm to 1 mm, morepreferably in the range of 0.08 mm to 0.6 mm. The u-bend width ispreferably in the range of 0.05 mm to 20 mm, more preferably in therange of 0.1 mm to 5 mm, and preferably the ratio of the cross-sectionalarea (height×depth) of u-bend inlet 235 to the cross-sectional area(depth×width) of u-bend 238 is in the range of 0.1 to 5. Too large au-bend width introduces large eddies into the comers and bottom of theu-bend, while too small a u-bend width may induce a new recirculationzone on the return path out of the u-bend due to boundary layerseparation.

[0166] Flow expansion at the tip 233 of the tongue will induce boundarylayer separation and a stagnation zone centered under the tongue. Theseproblems can be minimized by minimizing tongue height, t. Preferably,the tongue height is less than 1 mm, more preferably less than 0.5 mm,and still more preferably less than 0.2 mm thick. For economy ofconstruction and structural support, the tongue may have a constantheight, alternatively, the height can be tapered with the narrowestsection where the streams combine.

[0167] Combustion Jet Design

[0168] In some preferred embodiments, the heat source for theendothermic reaction is delivered directly to the wall in contact withthe endothermic catalyst. This follows from the fact that metalconduction is a more efficient mode of heat transfer than eitherconvective or radiative heat transfer.

[0169] In contrast to premixed combustion, where the heat release willoccur primarily in the homogeneous phase, combustion jets can direct aconcentrated stream of air into a separate fuel channel stream. The twostreams subsequently mix and undergo an oxidation reaction. In order tosuppress homogeneous combustion and promote heterogeneous catalyticcombustion on the channel wall, unique jet design features have beenimplemented. Important features include (1) geometry, (2) size, and (3)relative location and spacing.

[0170] The jets should not only impinge on the wall but also spread outthe combustion oxidant as uniformly as possible along the entire widthof the channel. Furthermore, heterogeneous combustion is preferablyconcentrated at the combustion wall in closest proximity to theendothermic reaction catalyst. Combustion on other walls represents aheat loss and furthermore has a disadvantageous impact on thermalstresses in the device.

[0171] In order to raise the temperature of an SMR reaction and reducethe likelihood of coke formation at the beginning of the reactor zone orin the heat exchanger zone reactant or product channels, more air shouldbe delivered for combustion against the wall at the beginning of thereactor zone. Concentration of jets in this region as well asapplication of non-circular jet orifices can successfully meet thisobjective.

[0172] All the goals above are desired to be accomplished with a minimalpressure drop for both economic reasons as well as for the purposes ofpreserving back pressure in the ICR device to ensure good flowdistribution. To this end, a hybrid of circular and rectangular slotorifices can be implemented in the jet design. Alternatively, othernon-rectangular non-circular jets could be used such as diamonds,triangles, semi-circles, quarter-moons, and the like. Computationalfluid dynamics (CFD) predictions indicate that a combination of thesetwo jet geometries provide a more ideal heterogeneous fuel-oxidantmixture distribution on the combustion channel wall opposite the jetshim. It is recognized that other non-circular jet orifices could alsobe used at the entrance of the combustion zone or anywhere down thelength of the reactor. It is also recognized that the combustionorifices could start before the reaction zone in the recuperative heatexchanger section to further preheat the reactants or further tailor thethermal profile of the device.

[0173] Control of the relative proportion of homogenous andheterogeneous combustion can be achieved by manipulation of the jetdesign. Either homogeneous or heterogeneous combustion can be increasedas needed depending upon the application. As an example, a microchannelcombustor that did not include an endothermic reaction may be enhancedvia jet design by promoting homogenous combustion to reduce hydrocarbonor CO emissions or to provide a hot gas stream for subsequent use in aunit operation.

[0174] While the examples show preferred embodiments in which theoxidant goes through the jets, it should be appreciated that fuel couldalternatively flow through jets to combine with an oxidant.

[0175] The distribution of jet orifices may depend on the intended useof the device. Hydrogen bums immediately, thus, to avoid hot spots, thejets should be spaced more evenly over the combustion chamber. Methane,which bums more slowly, preferably has jets loaded near the front of thecombustion chamber. When the fuel is syngas, the distribution of jets isintermediate.

[0176] The endothermic and exothermic reaction chambers preferablycontain catalysts. Catalysts suitable for catalyzing a selectedexothermic or endothermic reaction are well known to chemists andchemical engineers.

[0177] In some preferred embodiments of the present invention, catalysts(especially an endothermic catalyst) can be a porous catalyst. The“porous catalyst” described herein refers to a porous material having apore volume of 5 to 98%, more preferably 30 to 95% of the total porousmaterial's volume. At least 20% (more preferably at least 50%) of thematerial's pore volume is composed of pores in the size (diameter) rangeof 0.1 to 300 microns, more preferably 0.3 to 200 microns, and stillmore preferably 1 to 100 microns. Pore volume and pore size distributionare measured by Mercury porisimetry (assuming cylindrical geometry ofthe pores) and nitrogen adsorption. As is known, mercury porisimetry andnitrogen adsorption are complementary techniques with mercuryporisimetry being more accurate for measuring large pore sizes (largerthan 30 nm) and nitrogen adsorption more accurate for small pores (lessthan 50 nm). Pore sizes in the range of about 0.1 to 300 microns enablemolecules to diffuse molecularly through the materials under most gasphase catalysis conditions. The porous material can itself be acatalyst, but more preferably the porous material comprises a metal,ceramic or composite support having a layer or layers of a catalystmaterial or materials deposited thereon. The porosity can begeometrically regular as in a honeycomb or parallel pore structure, orporosity may be geometrically tortuous or random. In some preferredembodiments, the support of the porous material is a foam metal, foamceramic, metal felt (i.e., matted, nonwoven fibers), or metal screen.The porous structures could be oriented in either a flow-by orflow-through orientation. The catalyst could also take the form of ametal gauze that is parallel to the direction of flow in a flow-byconfiguration.

[0178] Alternatively, the catalyst support could also be formed from adense metal shim or foil. A porous catalyst layer could be coated on thedense metal to provide sufficient active surface sites for reaction. Anactive catalyst metal or metal oxide could then be washcoated eithersequentially or concurrently to form the active catalyst structure. Thedense metal foil or shim would form an insert structure that would beplaced inside the reactor after bonding or forming the microchannelstructure. Preferably, the catalyst insert contacts the wall or wallsthat are adjacent both the endothermic and exothermic reaction chambers.

[0179] The porous catalyst could alternatively be affixed to the reactorwall through a coating process. The coating may contain a first porouslayer to increase the number of active sites. Preferably, the porediameter ranges from tens of nanometers (for example, 10 or 20 nm) totens of microns (for example, 10 or 50 micrometers). An active metal ormetal oxide catalyst can then be sequentially or concurrently washcoatedon the first porous coating.

[0180] Preferred major active constituents of the catalysts include:elements in the IUPAC Group IIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB,IVB, Lanthanide series and Actinide series. The catalyst layers, ifpresent, are preferably also porous. The average pore size (volumeaverage) of the catalyst layer(s) is preferably smaller than the averagepore size of the support. The average pore sizes in the catalystlayer(s) disposed upon the support preferably ranges from 10⁻⁹ m to 10⁻⁷m as measured by N₂ adsorption with BET method. More preferably, atleast 50 volume % of the total pore volume is composed of pores in thesize range of 10⁻⁹ m to 10⁻⁷ m in diameter. Diffusion within these smallpores in the catalyst layer(s) is typically Knudsen in nature for gasphase systems, whereby the molecules collide with the walls of the poresmore frequently than with other gas phase molecules.

[0181] In preferred embodiments, catalysts are in the form of insertsthat can be conveniently inserted and removed from a reaction chamber.Reaction chambers (either of the same type or of different types) can becombined in series with multiple types of catalysts. For example,reactants can be passed through a first reaction chamber containing afirst type of catalyst, and the products from this chamber passed into asubsequent reaction chamber (or a subsequent stage of the same reactionchamber) containing a second type of catalyst in which the product (ormore correctly termed, the intermediate) is converted to a more desiredproduct. If desired, additional reactant(s) can be added to thesubsequent reaction chamber.

[0182] The catalyst (which is not necessarily porous) could also beapplied by other methods such as wash coating. On metal surfaces, it ispreferred to first apply a buffer layer by chemical vapor deposition,thermal oxidation, etc. which improves adhesion of subsequent washcoats.

[0183] The devices can be made by forming chambers within a single blockof material, by joining multiple components, and, most preferably, bystacking and bonding shims.

[0184] The aperture-containing shims can be formed by processesincluding: conventional machining, wire EDM, laser cutting,photochemical machining, electrochemical machining, molding, water jet,stamping, etching (for example, chemical, photochemical and plasma etch)and combinations thereof. For low cost, stamping is especiallydesirable. The shims may be joined together by diffusion bonding methodssuch as a ram press or a HIP chamber. They may also be joined togetherby reactive metal bonding or other methods that create a face seal.Alternately, laser welding shims could join the devices or sheets toform seals between flow paths. Devices could alternatively be joined bythe use of adhesives. In preferred embodiments, devices are laminated ina single step, in less preferred embodiments, a first set of shims isbonded together and subsequently bonded to a second (or more) set ofshims. In some preferred embodiments, a set of shims is bonded togetherin a single step and then the resulting bonded article is cut intomultiple devices.

[0185] Sacrificial Shims for Diffusion Bonding

[0186] Diffusion bonding of shims can create undesired channelcompression. Due to the high temperatures required for diffusionbonding, the material that is under load will inelastically deform tosome extent due to loading beyond its yield strength and creep strainduring the time required for bonding. Channel compression can bemitigated through the use of sacrificial shims placed on either side (oralternatively only one-side) of the shim stack and separated from theflow channels by at least one wall shim or wall plate. The sacrificialshim is generally described as a large open pocket that covers theotherwise open pockets in the shim stack. The sacrificial shim pockettakes up a portion of the deformation produced by the bonding force andgenerally is compressed after the bonding cycle. Sections of a shimstack wherein there is no material will not transfer any force.

[0187] In press bonding, the sacrificial shims absorb the deformationforces and help keep the internal dimensions consistent in the openareas which are used for operation. See FIG. 5 where the internal voidsare unaffected while the outer voids (sacrificial slots) aresignificantly deformed.

[0188] For any bonding method (axial pressing or isostatic pressing) ifthe open areas in the sacrificial shims are extended wider than theoperating channels, the ends of the channels are not loaded directly,and the change in length in the working channels is reduced. Thus,preferably, sacrificial voids extend further (for example, are longer)than the working channels they are protecting.

[0189] Sacrificial shims may take the form of one or multiple shims thatare stacked together or separated by solid walls. The sacrificial shimsmay be near the desired shim stack and separated by a single shim havinga thickness (height) of 0.25 mm or less. The sacrificial shims couldalternatively be placed a greater distance from the shim stack, or morethan 6 mm. Although sacrificial shims preferably are outside (that is,closer to a surface than) the process channels, sacrificial shims couldalso be placed elsewhere within the shim stack. In all cases, thechannels in the sacrificial shim are not in fluid contact with any ofthe streams that, during device operation, participate in the desireddevice unit operations. The chambers are vacant, or could alternativelybe later filled with a fluid to either promote or minimize thermallosses to the environment or to axial conduction along the length of thedevice.

[0190] The concept of sacrificial shims could also be extended toapplication in 3-D bonding methods such as HIP which also load the shimsperpendicular to the bonding direction. The sides of the shims could becovered with a shroud or an open pocket to take up the compressionduring bonding without deforming the desired channels. See FIG. 6. Inalternative configurations, the pockets could be formed in externalcomponents attached to the side of the shim stack, or pockets could beformed in each shim in the stack to create the sacrificial shroud.

[0191] In its broader aspects, the invention relates to any pair (ormore) of endothermic and exothermic reactions. For example, differentcompositions can be run through different reaction chambers havingdifferent catalysts. All of the examples and most of the description aredirected to gas phase reactions. However, the present invention couldalso be used for liquid phase reactions. In the case of liquid phasereactions, the critical channel dimension will likely be smaller thanthat for gas phase reactions to accommodate the reduced mass diffusionrate that brings reactants to the catalytic surface.

[0192] Catalytic processes (either exothermic or endothermic) of thepresent invention include: acetylation, addition reactions, alkylation,dealkylation, hydrodealkylation, reductive alkylation, amination,aromatization, arylation, autothermal reforming, carbonylation,decarbonylation, reductive carbonylation, carboxylation, reductivecarboxylation, reductive coupling, condensation, cracking,hydrocracking, cyclization, cyclooligomerization, dehalogenation,dimerization, epoxidation, esterification, exchange, Fischer-Tropsch,halogenation, hydrohalogenation, homologation, hydration, dehydration,hydrogenation, dehydrogenation, hydrocarboxylation, hydroformylation,hydrogenolysis, hydrometallation, hydrosilation, hydrolysis,hydrotreating (HDS/HDN), isomerization, methylation, demethylation,metathesis, methanation, nitration, oxidation, preferential oxidation,partial oxidation, polymerization, reduction, reformation, reverse watergas shift, Sabatier reaction, sulfonation, telomerization,transesterification, trimerization, and water gas shift.

[0193] One preferred endothermic reaction is steam reforming in whichwater (steam) and a hydrocarbon (or hydrocarbons) are reacted in anendothermic reaction chamber to form hydrogen and carbon oxides. Avariety of hydrocarbons can be reformed to produce hydrogen, includingmethane, ethane, propane, butane, isobutane, higher alkanes, alkenes,alcohols, ethers, ketones, and the like including blends and mixturessuch as gasoline, diesel, kerosene, and others.

[0194] For providing sufficient heat to an endothermic reaction, it ispreferred that the reaction in the exothermic reaction chamber be highlyexothermic. Combustion of hydrogen, CO, or a hydrocarbon (orhydrocarbons as listed above) is especially preferred.

[0195] It should be appreciated that in any of the devices describedherein, alternative reactants could be used in place of any of thereactants mentioned. For example, other fuels could be used in place ofmethane.

[0196] As described in greater detail below, preferred processes of theinvention can be described by the configuration of the apparatus and/orby measurable characteristics such as (but not limited to) heat flux,volumetric productivity, and/or pressure drop (which could also bedescribed in conjunction with process conditions such as flow rate,temperature, etc.).

[0197] Preferred reactors and methods of conducting reactions inintegrated reactors can be characterized by their properties. Unlessspecified otherwise, these properties are measured using the testingconditions described in the Examples section. The invention can becharacterized by any of the properties individually or in anycombination. Average volumetric heat flux is preferably at least 1 W/cc,or, in other preferred embodiments, at least 5, or 10, or 20, or 50, or100, and in some embodiments between 10 and about 120 W/cc. Theendothermic reaction chamber heat flux is preferably at least 10 W/cc,or, in other preferred embodiments, at least 50, 100, 200 or greaterthan 500 W/cc, and in some embodiments between 10 and about 700 W/cc.The devices can be characterized by the low NO_(x) output when measuredby the standard NO_(x) test measurement that is described in theExamples section. NO_(x) output is preferably less than 100 ppm, morepreferably less than 50 ppm, still more preferably less than 10 ppm, andstill more preferably less than 5 ppm, and in some embodiments, NO_(x)output is in the range of about 5 to 20 ppm. The inventive processesinvolving combustion preferably use less than 100% excess air (or,equivalently, excess oxygen), more preferably less than 75%, still morepreferably less than 50%, yet still more preferably less than 25%, or10% or 5% excess air. For characterizing devices, excess oxygen ismeasured under the conditions set forth in the Heat Flux MeasurementTest or (if characterized in conjunction with NO_(x) output) measuredunder the conditions set forth in the standard NO_(x) test measurement.Pressure drop through the exothermic and/or endothermic reactionchambers is preferably less than the following (in order of preference,based on length of reaction chamber) 295,000; 250,000; 125,000; 50,000;25,000; 12,500; 2500; or 1500 Pa/cm. For devices, the pressure drop ismeasured under the conditions set forth in the Heat Flux MeasurementTests.

[0198] Another advantage of the present invention is that good yields(or other measures of good performance) can be obtained with shortcontact times. In preferred methods, the contact time is less than 100milliseconds (ms), more preferably less than 50 ms, more preferably lessthan 25 ms, and still more preferably less than 10 ms, and in someembodiments between 1 and 25 ms for gas phase reactions. Liquid phasereactions would be expected to be at least three orders of magnitudeslower, thus necessitating longer contact times as compared to gas phasebut faster than conventional liquid phase reactions that have contacttimes ranging from minutes to days. Contact time may be reduced byreducing the diffusion distance between the bulk flow and the porouscatalyst while concurrently reducing channel length. At these contacttimes, in a preferred embodiment of hydrocarbon steam reforming, atleast 70%, more preferably at least 90%, of the absolute or equilibriumconversion of the hydrocarbon entering the beginning of said at leastone reaction chamber is converted to hydrogen, carbon monoxide and/orcarbon dioxide. Similar improvements can be obtained in other processes.

[0199] Some process characteristics of some preferred inventiveprocesses include the following: (1) Operate safely at a fuel:oxygenratio near stoichiometric (less than 100% excess air) for the use ofcombustion as the exothermic reaction. This reduces the required airwhich improves the overall system thermal efficiency and reduces therequired duty for the external air blower or compressor. (2) Operatesteam reforming at short contact times or conversely at high gas hourlyspace velocities. This is required to create a compact device. (3)Operate with a high heat flux. This is required to operate at shortcontact times. (4) Operate with a low pressure drop per unit length ofreactor. This enables a higher productivity per unit volume. (5)Optionally, quench/inhibit gas phase reactions. As the channel dimensionnears the quench diameter or drops below, then the contribution of theunwanted gas phase homogeneous combustion reaction is reduced.

[0200] In steam reforming, gas hourly space velocity is preferablygreater than 10,000, more preferably greater than 50,000, and may rangefrom about 100,000 hr⁻¹ to over 10⁶ hr⁻¹ corresponding to a contact timeon the order of 360 to 3.6 milliseconds, respectively. Operatingpressures for methane steam reforming preferably range from 1 atm to 50atm. A range of 1 to 30 atm is more preferred. Steam-to-carbon ratiosmay range from 1 to 10; a range of 1 to 3 is preferred.

[0201] Preferred Thermal Profile within the Reactor

[0202] The thermal profile within the integrated combustion reactor israrely isothermal. The temperature is typically coolest at the front ofthe reactor where the heat duty of the endothermic reaction is thehighest. The temperature is typically hottest at either the middle orend of the reactor, as defined by the direction of reactant flow. Insome preferred embodiments, it is desired to operate the reactor withthe hottest point near the end of the reaction chamber. Highertemperatures lead to increased metal expansion and thus it is desired tohave most expansion occurring at the free end of the device rather thanin the front end or in the middle of the reaction zone where the metalcan bulge. Minimization of thermal stresses in an ICR can be achieved bycreating a monotonically increasing thermal profile along the flowlength of the reactor. Preferably, temperature increases substantiallymonotonically in the direction of flow in both the exothermic andendothermic reaction chambers. In some cases, the temperature is notrigorously required to be hottest at the very end of the reactor, butshould have the hottest point in the last half of the reaction chamber.

[0203] The thermal profile can be controlled by placement of the airjets or apertures along the length of the combustion channel. Theplacement is affected by the combusting fuel. Hydrogen burns in a facilemanner and is best suited to a more even distribution of air thatincludes jets along most of the length of the reactor. Less facilecombustion fuels such as methane or natural gas requires more air towardthe front and center of the reactor and less toward the end. Methane ismore challenging to bum and requires additional time for air and fuel tocontact each other and bum along the length of the reactor.

[0204] An additional consideration in selecting the optimal thermalprofile within the reactor is the coking potential on the endothermicreaction. As an example, a steam reforming reaction with a relativelyhigh steam-to-carbon (>2.5:1) can tolerate a much cooler front endtemperature to avoid coking (<800 C.). A steam reforming reaction with arelatively low steam-to-carbon (<2.5:1) may utilize a higher front-endtemperature (>800 C.) to avoid coking. The coking potential can beweighed in conjunction with the thermal stresses to tailor both thefront end temperature and the slope of the increasing thermal profilealong the length of the reactor.

[0205] Preferred Characteristics: Element Preferred More Preferred Mostpreferred Endothermic at least 2.5 10 to 1000 200 to 600 chambervolumetric heat flux (W/cc) Volumetric heat at least 0.6 10 to 250 50 to120 flux (W/cc) Area heat flux at least 1 10 to 100 10 to 50 (W/cm2)Combustion dP <10 bar <3 bar <2 bar Endothermic <10 bar <3 bar <1 barreaction dP Combustion CT <100 ms <50 ms <25 ms Endothermic CT <500 ms<100 ms <25 ms NOx emissions <100 ppm <50 ppm <10 ppm CO emissions <2500ppm <1000 ppm <500 ppm Thermal efficiency >75% >85% >90% Excess air <50%<25% <10% Combustion >90% >95% >99% conversion (absolute) Combustionfuel H₂, methane, NG, hydrocarbon fuel Approach to Within 80% of Within90% of Within 95% of equilibrium on equilibrium equilibrium equilibriumendothermic reaction SMR conversion >50% >60% >70% SMR selectivityto >50% >60% >65% CO S:C on SMR side <4:1 <3:1 <2:1 SMR pressure <1000psig <500 psig <300 psig Pressure differential <900 psig, <500 psig,<300 psig >5 psig Time on stream >50 hours >200 hours >500 hours Heatexchanger flux >1 W/cm3 >2 W/cm3 >4 W/cm3

[0206] Low CO and NO_(x) are measured from the exhaust of the combustionreaction. The output of a reforming reaction can be controlled tomaximize H₂ production in which case, low CO selectivity is preferred,or syngas production, in which case, high CO selectivity is desired. Forhydrogen production, a CO selectivity is preferably 75% or less, morepreferably 68% or less and in some embodiments CO selectivity is in therange of 60 to 70%. “Pressure differential” refers to the pressuredifference between an endothermic reaction chamber and an adjacentexothermic reaction chamber.

[0207] Various startup procedures are described in the Examples section.

[0208] One method of conditioning (or refurbishing) a reactor, thatcontains a catalyst insert, includes steps of (1) raising the pressurein the reaction chamber that contains the insert, (2) lowering thepressure, and (3) operating the process. Pressure can be increased withthe process gas or an inert gas. Surprisingly, it was discovered thatthis conditioning step will sometimes significantly improve reactorperformance; perhaps this improvement is a result of the insert becomingbetter pressed against the reaction chamber wall.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS

[0209] FIGS. 8-22 are engineering drawings of shims for fabrication. Theshim shapes and dimensions shown in the drawings are illustrative butare not necessarily optimized and not necessarily from a single devicebut are intended to represent shim designs of devices that weremanufactured and tested. Some of the figures may contain distances ininches and related lines or partial lines—these are artifacts of thedesign purposes of the figures and may be deleted.

[0210] Bonded ICR Device—Two-Stream Loop

[0211] In this embodiment, a single integrated device contains a reactorzone, a preheat or recuperative heating zone, and a manifold zone.

[0212] The device is characterized by a free-end to allow for thermalexpansion and stress minimization at the hottest end of the device. Tocreate a free-end, the reactant stream makes a U-bend to form theproduct stream. The combustion stream (combined fuel and air) makes aU-bend to form the combustion exhaust stream.

[0213] The flow orientations are characterized by a two-stream loopgeometry. A reaction layer contains a reactant channel that flowsthrough a manifold zone, through a pre-heat zone, and then into thereaction zone within the same reaction microchannel. This processreaction stream then makes a U-turn into a product return stream thatflows countercurrent to the originating reaction channel. On the otherside of the product return stream, a second reactant channel flows in acounter-current manner. At the top of the U-bend, the two processreaction channels join to form the common product return channel downthe center. As the two process reaction streams merge into a singleproduct return stream, there is an interspaced tongue to prevent directflow impingement and corresponding instabilities.

[0214] Adjacent to the process layer, is a combustion layer. Theoutermost channels are comprised of a fuel channel. Fuel flows through amanifold layer at the bottom of device, then through the preheat orrecuperative heat exchanger zone in a contiguous microchannel, and theninto a combustion reaction zone. Air flows adjacent to each of the fuelchannels through the manifold and exchanger zone. Air is then bled intothe combustion zone through the use of jet orifices to meter air alongthe length of the combustion zone. The air channel stops before theU-bend section. The two fuel channels are joined near the end of thecombustion zone. The two streams are merged into a single exhaustchannel that flows down the innermost channel of the combustion layer.As the two combustion streams merge into a single exhaust return stream,there is an interspaced tongue to prevent direct flow impingement andcorresponding instabilities.

[0215] The process reaction and combustion layers may be repeatedmultiple times to achieve the desired capacity. The terminating layer ofthe repeating unit is characterized by a single process reactionchannel, adjacent to the combustion zone, which makes a U-bend into aproduct return channel that comprises flow from a single reactantchannel. Flow in this outermost layer is half that in the innerrepeating process layers.

[0216] The recuperative heat exchanger zone is comprised of 5 fluidsthat exchange heat. The repeating channels are as follows: product,reactant, fuel, air, exhaust, air, fuel, reactant, product, reactant,fuel, and so on. Heat from the product and the combustion exhauststream, preheat the reactant, combustion fuel, and combustion air.

[0217] The five streams are manifolded at the cold end of the device.One fluid is manifolded directly out the bottom of the device. The otherfour streams are divided two per side. Each of the five manifold areasare then connected to external pipes to bring or remove fluids to orfrom the device.

[0218] A typical ICR is made from numerous shims; for example an ICR hasbeen constructed from the 63 shim stack shown in FIG. 7 (this device issometimes referred to as a two-stream loop device). A partly explodedview of this device is illustrated in FIG. 8. The shim stack includedsacrificial shims 82 located adjacent end plate 86. During the bondingprocess, the sacrificial shims deformed, relieving stress from theapplied bonding pressure and reducing deformation of the processchannels. The shims have a length of about 21 inches (53 cm), a width ofabout 1.4 inch (3.6 cm) and variable thicknesses (heights) ranging fromabout 0.25 mm to about 0.64 mm, and endplates as thick as 6.4 mm.Endothermic reaction channels are 9.7 mm wide. Air, fuel, exhaust, andtwo-stream loop product channels are 4.1 mm wide. There are two of eachof these channels for every endothermic reaction channel. Single-streamloop channels on the outermost edges contain two product channels thatare 33 mm wide.

[0219] The two-stream loop device was made using Alloy-617 metal shimsthat were diffusion bonded together to form a microchannel reactor. TheAlloy-617 shims were initially formed by a combination of laser cuttingand wire-EDM. Prior to having shims cut, the sheets of material wereinitially coated with an average 300-micro inch layer ofNickel-sulfamate (Acteron, San Carlos Calif.). End plates were madeusing conventional machining and they were also coated with an average300-micro inch layer Nickel-sulfamate coating. The cut shims and coatedendplates were cleaned in a denatured alcohol bath for several minutesand then wiped dry. Two different sets of shims were laser welded topreseal the air microchannel prior to diffusion bonding. The stackedshim set was diffusion bonded using a vacuum ram press at 1150° C. andapproximately 29,700 force-pounds for 6 hours.

[0220] The diffusion bonded part was then machined using a plunge-EDM toopen the slots on the sides and top of the device. The externalmanifolds for the air, fuel, and the SMR reactant and product lines werethen TIG welded. The device was then cleaned by first pumping hexaneinto the device, soaking for 5 minutes, then pumping hexane through allthe channels until it came out clean. The device was then purged withargon, and the procedure repeated using 20% nitric acid. Then de-ionizedwater was pumped through the device until the pH was >5, after whichethanol was pumped through the device for 30 seconds. Finally, thedevice was purged with argon for 5 minutes at a flow of ˜10 SLPM. Thecleaned device was then heat treated and washcoated with combustioncatalyst (as described in the examples section). The oxide formed on thecatalyst door and plugs was removed via grinding near the welding edge.The SMR catalyst was then loaded in the device. The exhaust manifold waswelded to the device.

[0221]FIG. 9A shows one side of a partly assembled ICR 91 with slots 93and 95. A view of the opposite side is shown in FIG. 9B with slots 97and 99. The circled sections indicate the sections that are manifoldedto handle flows into and out of the ICR. End 92 has catalyst insertionports (described in greater detail below) and end 94 has exhaust ports(not shown) that feed into an exhaust manifold.

[0222] The insertion of catalyst inserts is schematically illustrated inFIG. 10. Each catalyst subassembly 102 is slid into insertion slot 104and supports 106 brace the catalyst insert 108. After the catalysts areinserted, catalyst doors are inserted into each slot (the doorssubstantially blocking flow) and a slotted cap (not shown) was weldedonto end 105 and the slots in the cap are welded closed, thus sealingone end of the endothermic reaction channels.

[0223]FIG. 11 is an exploded view of the manifold end illustrating fuelinlet 101, reactant inlet 102, air inlet 103, product outlet 104, andexhaust 105. Each of these tubes was welded into the correspondingmanifolds 111-115. Reactant flows into reactant channels throughreactant inlets 116 while fuel flows in through fuel inlets 117.

[0224] At the other end of the device (see FIG. 12) are catalyst accessports 121. Catalyst doors 122 are slid in through the access ports. Thecatalyst doors are metal strips that are sized to fit into catalystchannels and hold the catalyst insert in place. In one device, thecatalyst doors had dimensions of 50 mm×10 mm×0.5 mm. A cap 123 is placedover the end of the device and grooves 126 were plugged prior tooperation. Tubes 124 connect into catalyst precursor access ports 125and provide for a combustion catalyst precursor composition.

[0225]FIG. 13 illustrates a 0.64 mm thick combustion shim of the typeused in Example 2. The shim has flow channels 132 separated by ribsupport 133. During operation, fuel enters through the right, travelsthrough the flow channels and exits through outlet 134. Metal area 135is removed after bonding. Like all shims except one endplate, the shimcontains catalyst precursor passages 136. Notches are cut into thecombustion shim to receive and hold in place flow stabilization insertsimmediately (˜1 mm) upstream of the first air jet. The device of Example2 included a porous flow stabilization insert in each fuel channelimmediately upstream of the first point of air injection. These porousinserts were made from rectangular pieces of FeCrAlloy foam (˜95 poresper inch) measuring 0.7 mm thick, 13 mm long (flow direction) by about 5mm wide, although other materials of construction could be used toaccomplish the same purpose.

[0226]FIG. 14 illustrates a 0.25 mm thick shim containing endothermicreaction channel 141 that is similar to the combustion shim except thereaction channel does not have a rib support.

[0227]FIG. 15 illustrates a welded subassembly containing a 0.64 mmthick air shim 151 containing air channels 152 sandwiched between wallshim 153 (0.25 mm thick) and jet shim 154 (0.25 mm thick). In the ICRdevice of Example 1, the jet shim contained 28 circular orifices withthe first four jets near the beginning of the reactor zone (1 mmdownstream) and the last two jets about 0.75″(19 mm) upstream of thecombustion u-bend. The circular orifices had a diameter of approximately0.31 mm with non-uniform center-to-center spacing along the length ofthe combustion channel. Along the width of the channel the orifice pairplacement is alternately staggered on “quarter centers”, i.e., ¼ and ¾across the width of each of the channels in the combustion shim or 1.02mm and 3.05 mm across each 4.06 mm wide channel. In the 28 jetconstruction, the first four jets (farthest upstream) were placed onboth quarter centers of both channels on each jet shim and the remaining24 jets staggered alternately as described above along the length of thereactor zone. Specifically, the orifice placement for the 28 jetconstruction was in pairs along the length of the reaction zone atlocations of 1 mm (four jets) and 8, 15, 24, 34, 46, 58, 72, 87, 104,122, 142, and 160 mm from the plane of the leading (upstream) edge ofthe SMR catalyst, staggered on quarter centers. In the ICR device ofExample 2, the jet shim contained only 24 circular orifices atincreasing intervals along the length of the reactor zone. Specifically,the orifice placement for the 24 jets were in pairs along the length ofthe reaction zone at about 1, 8, 15, 24, 34, 46, 58, 72, 87, 104, 122,and 142 mm from the plane of the leading (upstream) edge of the SMRcatalyst, staggered on quarter centers.

[0228] The shims include alignment hole 155 and exhaust passages 156.The exhaust passages were isolated by laser welds 157. The air shim 151contains a connecting channel 159 between the catalyst precursor pathwayand the exhaust passages 156; after bonding, a catalyst precursorcomposition flows into the exhaust passages 156 and then into theexhaust and combustion channels. During the deposition of the combustioncatalyst, the device was oriented with respect to gravity such that thecatalyst precursor filled only the desired length (in this case, about18 cm) of the combustion and exhaust channels.

[0229] In an alternate construction (such as that used in Example 1) a0.41 mm thick combustion shim 165 is illustrated in FIG. 16A thatcontains a solid heat transfer region 161 and combustion region 162containing combustion channels 163. The combustion channels 163 provideadditional volume for a combustion reaction that runs over the length ofthe combustion channel (7 inch, 18 cm). Shim 160 is bonded to 0.25 mmthick combustion shim 166 (see FIG. 16B) which has continuous flowchannels 169. In this construction, each shims 165 and 166 together forma combustion channel that is more narrow in the preheat zone andprovides combustion flow stabilization during operation (as discussed inthe Examples section), eliminating the need for a flow stabilizationinsert. When this construction is used, shim 166 is stacked adjacent tothe wall nearest to the air channel shim while shim 165 is stackedadjacent to the wall nearest to the endothermic reaction channel shim.

[0230]FIG. 17 illustrates a 0.64 mm thick air channel shim. Air entersthrough inlet 171 (metal strip 172 is cut off after bonding) and fillsthe length of channels 173. Dividing rib 174 has a width of 0.06 in (1.5mm). Separate from, and unconnected to, the air channels 173 are u-bendpassages 175 and catalyst precursor passages 176.

[0231] An exhaust channel shim 181 is illustrated in FIG. 18. A supportrib 182 separates the channels, and catalyst precursor passages 183 arealso present. Section 184 is removed after bonding to form a path to theexhaust manifold. Typically 3 similarly configured exhaust shims arestacked (i.e., 3 consecutively stacked exhaust shims) to form theexhaust channel and tongue. The shim thicknesses (height) of the exhaustchannel shims in the order they are stacked is 0.36, 0.25, and 0.36 mm.The middle shim in the 3 shim exhaust stack forms the tongue feature andhas a slightly shorter channel length, stopping about 5 mm short of theu-turn.

[0232] A 0.25 mm thick catalyst stop shim 191 (for the endothermiccatalyst) is illustrated in FIG. 19. This shim contains a 188 mm channel192 that holds in place the catalyst insert. Metal strip 193 is removedafter bonding. FIG. 20 illustrates a shim (0.25 mm thick) that forms awall for the endothermic reaction channel and separates the endothermicreaction channel from the endothermic product channel. A u-bend passage199 allows passage of endothermic products.

[0233]FIG. 21A illustrates a product channel shim 195 (0.25 mm thick).The illustrated shim has 4.5 inch (11 cm) channels 196 and is laserwelded to the endothermic wall shim of FIG. 21B. FIG. 21B illustrates asecond product channel shim (0.41 mm thick) with 44.3 cm channels 207.Product shim 208 forms the product channel tongue and is stacked betweentwo product channel shims 195. In these channels, product enters at 197from the u-bend aperture in the adjacent shim and then flows intoendothermic product channel 207 in an adjacent shim 208. In theoutermost product channels, where only a single reactant channel feedsthe product channels, a slightly thinner product channel shim (0.36 mmthick) is used similar to product channel shim 208 (FIG. 21B) but with alonger channel, extending the entire 47 cm from the u-turn to theproduct manifold.

[0234] Welded ICR Devices—N and M Types have Essentially the SameStructure but Differing Catalysts

[0235] A welded ICR was constructed from Inconel Alloy-617 and 625. Allparts were made from a combination of conventional machining, wire EDM,and laser cutting. All parts were cleaned with hexane and heat treated.Oxide was removed via grinding near the weld edge, recleaned in alcoholand stacked. The device was perimeter welded using TIG welding. Tubingwas welded to the device to form connections for air, fuel, exhaust,reactant and product.

[0236]FIG. 22A shows an exploded view of the welded ICR. In theassembled device, fuel enters through fuel inlet 223. After welding thedevice, a steam methane reforming catalyst (including a metallic feltsupport) was placed into catalyst slot 225. The device was made bywelding endplate 227 (⅜ inch thick with 0.014 inch channels), air shim229 (20 mil air channel covered by a jet plate), fuel channel shim 231(25 mil thick with channel machined through shim), endothermic reactionshim 233 (0.105 inch thickness including a 24 mil rib (not shown) thatprojected into the air channel, a 10 mil deep reactant channel, and 20mil deep endothermic reaction chamber 225. For the N2 construction, 2inches of the rib were machined off shim 233 and a Pox catalyst insertedinto the fuel channel. Catalyst support strips 217 were tack welded inand contacted u-bend shim N19 and pressed the catalyst (not shown)against the wall of reaction chamber 225 which typically contained a 12mil thick catalyst insert. U-bend shim 219 contained a u-bend orificehaving dimensions of 60 mil×380 mil. The other end plate was identicalto 227 except the channels were 30 mil deep.

[0237]FIG. 22B shows a partially exploded view of the welded ICR-Ndesign including product tube 20, air tube 22 and air manifold 24,exhaust tube 26, endothermic reactant tube 28, manifold 30, fuel tube 32and manifold 34. In this tested device, outer plate 36 contains holes 38for inserting thermocouples to monitor gas temperature.

[0238]FIG. 22C shows that the two shims that make up welded jetsubassembly 229. Conventionally machined air channel shim 220 has airchannels 222 and exhaust u-bend 224. Jet shim 226 was laser welded overthe air channel shim to form subassembly 229. This laser welding stepforms a seal along the entire perimeter of the jet shim except at theair inlet on the manifold end, thus preventing the fluid in the airchannels from bypassing the jet holes during operation. Duringoperation, air from the jet subassembly passes through the jet holes andshoots against the catalyst-coated wall of the combustion channel thatis adjacent the endothermic catalyst insert—thus causing combustion atthe wall and maximizing the rate of heat transport into the endothermicreaction. The air channel shim had a thickness of 0.64 mm and the jetshim had a thickness of ˜0.30 mm. The jet shim contained 2 slot orificesof approximate dimensions 0.31 mm by 0.91 mm including full roundscentered across the width of the channel at the beginning of the reactorzone. The first slot jet is oriented with the long dimension in thedirection of flow (in the axial direction) whereas the second slotorifice is oriented with the long dimension orthogonal to the directionof flow. These two slots are followed by 10 circular orifices have adiameter of approximately 0.31 mm on staggered quarter centers. Thefinal 2 orifices just upstream of the U-bend are paired on centeredquarters with an approximate diameter of 0.31 mm. Non-uniform spacing isemployed between successive jets.

[0239] Catalyst Insertion in Bonded Devices

[0240] The SMR catalyst inserts were in the form of a 178 mm longsection of FeCrAlY felt coated with active catalyst material. The insertwas nominally 0.25-0.30 mm thick and 9.4 mm wide. Alternatively, thinneror thicker materials could have been used, as well as wider or narrowersections of felt.

[0241] The catalyst section was inserted into the bonded integrated ICRreactor with an insertion tool. The insert included two metallic spacers(Inconel 625, 0.2 mm×0.2 mm cross section) that are held at each side ofthe felt to ensure that it sits against a channel wall while alsomaintaining an open gap for gas to flow adjacent to the catalyst.

[0242] The major components of the insertion tooling are the holdingfixture, the pressure differential guide assembly and the pusherassembly. The holding fixture holds the device in position during thecatalyst insertion. The pressure differential guide assembly contains achannel to hold the catalyst and spacers in position. It provides aguide for an insertion tongue which provides a vacuum to hold thecatalyst and spacer assembly sandwich in place during insertion. Thepressure differential guide assembly locates a pressure differentialover the sandwich and provides a guide for the pusher assembly. Thepusher assembly is a worm gear slide assembly. A direct currentcontrolled stepper motor is used with pressure feedback to insert thecatalyst.

[0243]FIG. 24A shows a schematic plan view of the insertion tool. Thespacers (245 in FIG. 24B) are loaded into channels 242, 244. Vacuum isapplied through holes 246 to hold the spacers in place. The catalyst(not shown) is placed over the tongue 248 and spacers. A plate (notshown, having a thickness of 0.5 inch; the plate supports the top of thecatalyst insert so that it does not buckle when being pushed into amicrochannel) is placed over the sandwich created by the spacers andcatalyst and catalyst is then pushed into the device. The side of thedevice is indicated schematically by the block labeled “device” and theinternal channel is indicated by dashed lines. Tongue 248 is 6 mil (0.15mm) thick and the pressure differential guide assembly is about 0.5 inch(1.2 cm) wide.

[0244] The bonded ICR reactor is placed within a holding fixture andclamped in place. The catalyst and spacers are concurrently insertedinto the device with the aid of the tooling (see FIGS. 24A-C) thatcontinuously applies a vacuum along the length of the catalyst sectionand spacer assembly. The vacuum ensures that the catalyst is held inplace. The vacuum holding the spacers is released and the tongue whichholds the catalyst in place via vacuum is then inserted into thenominally 20 mil high channel for the entire 7″ (18 cm) length of thereaction channel. The pressure differential guide assembly and plateremain outside the device. The pusher assembly has an automated featureto monitor pressure or load down the length of the channel. This ensuresthat the catalyst does not snag against a wall. When the catalyst hasreached the end of the entire 7 inch reaction chamber, the vacuum isstopped and the catalyst releases to be adjacent to the wall. The vacuumacts to slightly compress the porous catalyst and when released, thecatalyst expands and the catalyst and spacer assembly create a snug fitwithin the reactor.

[0245] Manifolding

[0246] The integrated ICR reactor system contains five distinct fluidstreams connected to the device: process reactant in, process producteffluent, air inlet, fuel inlet, and exhaust outlet. One fluid stream(exhaust) exits the bottom of the device. Alternatively, any of theother streams could be manifolded out the bottom, or cold end, of thedevice. The exhaust stream was selected to exit through the bottom ofthe device to minimize overall pressure drop. An external manifold iswelded on the bottom of the device to connect the flow path to a pipefor easy connection in the testing infrastructure.

[0247] The four remaining streams are manifolded on the sides of thedevice. Each fluid enters or exits along the sides of the shims. Thefluid streams enter or exit at different levels along the length of theICR. Each fluid is self-contained within a shim or several adjacentshims and does not break through the plane of a wall shim that separateseach of the fluids within the device. There is no opportunity for aninterstream leak except at the edge of the device if the externalmanifolds are not properly joined and sealed or if the shims are notproperly joined and sealed in the area between the catalyst precursorpathways and the reactor fluid channels. Alternatively, streams could bemade to share a common shim within the device, but this placesadditional challenges in manifolding and sealing streams.

[0248] For multi-stream devices, fluids may enter or be withdrawn atdifferent heights of the device. This allows ease of manifolding whilepreventing interstream leakage as well as allowing for tailoring of thethermal profile of the exchanger. Streams that enter the device muchwarmer than other streams may be selected to be manifolded farther downthe length of the device, or into the warmer section of the recuperatorzone.

[0249] The air stream was manifolded from approximately 13 mm from thebottom of the ICR to approximately 64 mm from the bottom of the device.In this discussion, the device is viewed standing on one end with thefluid inlets and outlets on the bottom. However, the open slots allowingthe air into the bonded device were only about 13 mm tall and allow thechannels to turn approximately 90 degrees as it enters the integratedmulti-stream recuperator zone. The height of the opening for air orother fluids is selected to generally minimize overall pressure drop.Smaller heights could be selected if higher pressure drops wereallowable. Similarly if lower pressure drops were desired, then theinlets and outlets could be positioned closer to the reaction zones.

[0250] The fuel stream enters the device also approximately 13 mm fromthe bottom of the device to approximately 64 mm from the bottom of thedevice. The fuel was manifolded however on the opposite side of the ICR.The fuel enters along different planes from the air and is separatedfrom all other streams via interleaved containment walls.

[0251] Farther along the length of the device, the process reactant andproduct were manifolded on opposing sides of the device. At roughly 7.5to 11 cm from the end of the device, the product streams either enter orexit the device, respectively. External manifolds were welded on theoutside of the device to join each like stream, and the manifolds joinwith external pipe connections. Each stream enters from the side andmakes an approximately 90 degree turn before flowing straight throughthe device. The stream stays within the same microchannel from the timeit enters the device, through the exchanger zone, through the reactorzone, around the U-bend, back through the exchanger zone, and then itexits as the process product effluent along a different plane and outthe side on the opposing face of the hardware.

EXAMPLES

[0252] Preparation of the engineered steam reforming catalyst used inthe Examples consists of catalyst powder preparation, slurrypreparation, FeCrAlY felt preparation, and engineered catalystpreparation. The procedure for each step is described as follows:

[0253] Catalyst Powder Preparation:

[0254] Catalyst powder used for the steam reforming consists of 10 wt %Rh/4.5 wt % MgO/85.5 wt % Al₂O₃. The specific details of samplepreparation are described below.

[0255] 1) Spinel Support Synthesis

[0256] 1. Grind a neutral gamma-phase aluminum oxide, Al₂O₃ (≧0.8cc/gram and ≧200 m²/gram), and sieve to +100-mesh

[0257] 2. Calcine the alumina powder at 350° C. for 3-hours at a ramprate of 5° C./min

[0258] 3. In a container, add a known volume of the magnesiumimpregnation solution dropwise onto the alumina powder in a quantitysufficient to produce incipient wetness of the powder

[0259] 4. The magnesium impregnation solution is made by dissolvingsufficient quantity of magnesium (II) nitrate hexahydrate (99%),Mg(NO₃)₂.6H₂O, in deionized water (at room temperature) which is thendiluted to a volume (after dissolution of the precursor salt) of 1.87-mLper gram of precursor, using a shaker or ultrasonication to aid indissolution

[0260] 5. Mix/blend the powder continuously during impregnation

[0261] 6. After impregnation, continue to mix and/or shake the catalystpowder for ˜15-minutes

[0262] 7. Spread out and dry the catalyst powder at 100° C. for ˜24-hrs

[0263] 8. Lightly re-crush the dried catalyst to break-up anyagglomeration that occurs during drying

[0264] 9. Calcine the dry spinel catalyst powder at 900° C. for 2-hoursat a ramp rate of 5° C./minute

[0265] 2) Catalyst Synthesis

[0266] 1. In a container, add a known volume of the rhodium impregnationsolution (rhodium nitrate solution, ˜10 wt % from Engelhard) drop wiseonto the spinel powder in a quantity sufficient to produce incipientwetness of the powder

[0267] 2. Mix/blend the powder continuously during impregnation

[0268] 3. After impregnation, continue to mix and/or shake the catalystpowder for ˜15 minutes.

[0269] 4. Spread out and dry the catalyst powder at 100° C. for ˜24-hrs.

[0270] 5. Calcine the dried catalyst powder at 500° C. for 3-hours at aramp rate of 5° C./minute

[0271] 6. Re-sieve the catalyst powder to +100 mesh

[0272] 7. This should produce a catalyst powder with a composition ofabout 10-wt % Rh, 6-wt % MgO, and 84-wt % Al₂O₃.

[0273] Catalyst Slurry Preparation:

[0274] Catalyst slurry is used to coat the engineered substrate material(FeCrAlY felt), which consists of finely milled steam reforming catalystin deionized water at a certain water-to-catalyst ratio.

[0275] 1. Combine the catalyst powder with deionized water in awater-to-catalyst weight ratio of about 6.5:1 and place in a ceramicmilling container with 3-mm (diameter) high-purity alumina sphericalgrinding media in a media-to-catalyst weight ratio of about 20:1

[0276] 2. Place on a ball mill grinder (U.S. Stoneware, Model 755 RMV)at the highest speed possible without cascading occurring in the millingcontainer

[0277] 3. Ball mill for 24-hours

[0278] 4. Separate out the slurry from the milling media using atransfer pipette

[0279] FeCrAlY “Felt” Preparation:

[0280] Substrates such as FeCrAlY felts are used as the support materialfor engineered catalyst (Technetics, Deland, Fla., 0.25 mm thicknesswith a porosity of 75%). Such supports are cleaned and heat-treated togrow a thin oxide layer. Subsequently, the support was coated with asub-micron layer of alumina using chemical vapor deposition (CVD)technique to protect the substrate from corrosion under hydrothermalconditions and to provide an inert surface.

[0281] 1. Cut the FeCrAlY alloy “felt” (nominally 0.25 mm thick) to thedesired dimensions, using either mechanical, wire electrical dischargemachining (wire EDM) or laser-cutting techniques. The required catalystsupport dimensions were 11.9 mm×88.9 mm for the devices of Examples 3and above (two catalysts were laid end to end to cover the 178 mmreaction chamber length) [welded ICR M and N devices] and 9.4 mm×178 mmfor the devices of Examples 1-2 [bonded ICR devices].

[0282] 2. Clean felts ultrasonically in acetone and then 2-propanol for20 minutes each.

[0283] 3. Dry felt pieces at 110° C. for 30 minutes.

[0284] 4. Place the cut felt pieces in a furnace in air and heat to 900°C. at a rate of 20° C./min and hold at 900° C. for 2-hours, then allowthem to cool to room temperature slowly (˜20° C./min)

[0285] 5. Flow N₂ gas containing aluminum oxide precursor such asaluminum alkoxide, particularly aluminum isopropoxide over theheat-treated felts in an oxidizing environment containing 14 vol % of O₂under 5 Torr at 850° C. for 1.5 hours in a CVD chamber.

[0286] Engineered Catalyst Preparation

[0287] Engineered catalyst is prepared using a dip coating method toachieve a target weight gain of 0.1 g/in².

[0288] 1. Dip the felts into the catalyst slurry under agitation; makingsure entire felt is immersed at one time

[0289] 2. Pull the felt out and allow excess slurry to drop out, wipingexcess on the rim of the container if necessary

[0290] 3. Dry the catalysts at 100° C. for 1 hour

[0291] 4. Repeat 1-3 until a loading of about 0.1-grams of dry catalystper square inch of metal felt substrate is achieved

[0292] 5. Calcine the dried engineered catalysts according to thefollowing temperature program:

[0293] Ramp to 350° C. at a rate of 5° C./min and hold at 350° C. for 3hours

[0294] Cool slowly to room temperature (˜5° C./min)

[0295] Combustion Catalyst

[0296] To coat the combustion catalyst in the devices of Examples 1-2,the device was heat treated in flowing air by ramping from roomtemperature to 1000° C. at 3.5° C./minute and then holding at 1000° C.for 3 hours. The device was then allowed to cool to room temperature ata slow ramp rate of 3.5° C./minute. The device was then flushed with DIwater for particulate removal. The device was then heat treated again inflowing air by ramping from room temperature to 1000° C. at 3.5°C./minute and then holding at 1000° C. for 1 hour. The device was thenallowed to cool to room temperature at a slow ramp rate of 3.5°C./minute. Throughout the heat treatment, hydrocarbon-free air from acylinder was used to purge the device at a flow rate of 150 cc/min.

[0297] Then, syringe pumps were used to flood the device through thecatalyst precursor passageways with a known volume of an aqueoussolution of Ce and Pd salts at a Ce:Pd ratio of 4:1. 14.32 cc of Ce/Pdsolution was needed to flood the device to a height of 7 inches (18 cm).After the desired volume of solution was flooded into the device, thesolution was allowed to equilibrate for 2 minutes before being drained.Nitrogen was used to purge the device to ensure that the air holes werecleared from catalyst solution. Purging was done with nitrogen flowingfrom the combustion channel to the air channel The device was calcinedin flowing air by ramping from room temperature to 850° C. at 3.5°C./minute and then holding at 850° C. for 1 hour. The device was thenallowed to cool to room temperature at a slow ramp rate of 3.5°C./minute. Throughout the heat treatment, hydrocarbon-free air from acylinder was used to purge through the device at a flow rate of 150cc/min.

[0298] Combustion catalyst was applied in the welded ICR-M devices asfollows. Shims were heat treated in air by ramping from room temperatureto 1000° C. at 3.5° C./minute and then holding at 1000° C. for 1 hour.Shims were then allowed to cool to room temperature at a slow ramp rateof 3.5° C./minute. The shim surfaces of the combustion zone were coatedwith an aqueous solution of Ce and Pd salts at a Ce:Pd ratio of 4:1. Acotton applicator was used to brush the solution onto the shims. A totalof 3 coats were applied. The assembly was purged with compressednitrogen to ensure that the air holes were fully cleared before drying.A drying step was conducted after each coating (about 80 to 100° C. for30 to 240 minutes). Shims were calcined in air by ramping from roomtemperature to 850° C. at 3.5° C./minute and then holding at 850° C. for1 hour. Shims were then allowed to cool to room temperature at a slowramp rate of 3.5° C./minute.

[0299] Shims were heat treated in air by ramping from room temperatureto 1000° C. at 3.5° C./minute and then holding at 1000° C. for 1 hour.Shims were then allowed to cool to room temperature at a slow ramp rateof 3.5° C./minute.

[0300] Combustion catalyst was applied in the welded ICR-N devices asfollows: the shim surfaces of the combustion zone were coated with anaqueous solution of Ce and Pd salts at a Ce:Pd ratio of 4:1. A cottonapplicator was used to brush the catalyst solution onto the shims. Atotal of 3 to 6 coats of Ce/Pd solution were applied. In between coats,the shims were dried at 100° C. for 1 hour. 1 coat of an aqueous Pt saltsolution was added and followed by drying at 100° C. for 1 hr. Shimswere calcined in air by ramping from room temperature to 850° C. at 3.5°C./minute and then holding at 850° C. for 1 hour. Shims were thenallowed to cool to room temperature at a slow ramp rate of 3.5°C./minute. For the welded ICR-N3 device, a pre-mixed La—Al₂O₃—ZrO₂powder slurry was applied onto the surfaces of the combustion zoneforming a coating of catalyst support. The shims were dried at 100° C.for 1 hour. Shims were then calcined in air by ramping from roomtemperature to 1000° C. at 3.5° C./minute and then holding at 1000° C.for 1 hour. Shims were then allowed to cool to room temperature at aslow ramp rate of 3.5° C./minute. A Ce/Pd solution was applied onto theLa—Al₂O₃—ZrO₂ support that was previously coated in the combustion zoneon the shims. A total of 3 Ce/Pd coats were applied. In between coats,the shims were dried at 100° C. for 1 hour. Shims were then calcined byramping from room temperature to 1000° C. at 3.5° C./minute and thenholding at 1000° C. for 1 hour. Shims were then allowed to cool to roomtemperature at a slow ramp rate of 3.5° C./minute 1 coat of an aqueousPt salt solution was then applied. The shims were dried at 100° C. for 1hour. Shims were then calcined in air by ramping from room temperatureto 900° C. at 3.5° C./minute and then holding at 900° C. for 1 hour.Shims were then allowed to cool to room temperature at a slow ramp rateof 3.5° C./minute.

[0301] Bonded ICR Examples 1 and 2

[0302] The microchannel ICR reactor system in these examples had thetwo-stream loop design described in the above section entitledDescription of Preferred Embodiments. The streams entering the devicemay either be at ambient conditions or at a slightly elevatedtemperature. A series of microchannel exchangers were optionally used toprovide additional preheat to the streams.

[0303] A multi-channel bonded ICR device was designed, fabricated, andoperated for over 300 hours. This device was formed from stacking metalplates of various thicknesses (0.25, 0.36, 0.41, 0.51, 0.64, and 6.4 mm)with various portions cut away to form channels for flow of the severalfluid streams and diffusion bonding the stack together, with thickerplates placed in the outermost edges of the stack of plates (likebookends). The device included 3 exothermic reaction (combustion)repeating units flanked by endothermic reaction (SMR) channels.

[0304] The process side of this diffusion bonded device was operatedwith an SMR contact time of 9 ms, 2.5:1 steam:C, about 865 C., and 12atm SMR outlet pressure. The combustion side of was operated with a fuelcomposition of 5-10% CH₄ and 6-9% CO₂ (balance H₂) with 5-10% excessair, and about 7 psig outlet pressure (due to losses in valves andequipment downstream of the device). The gas chromatograph calibrationwas checked every 8 hours and was recalibrated as needed.

[0305] Installation/Startup

[0306] The process reactant was preheated to 260 to 290 C. using amicrochannel exchanger system consisting of two types of exchangerswhich include an array of parallel microchannels. Type 1 was a singlepass exchanger containing 50 microchannels which were 2.5 mm×64 mm×0.25mm and heated with a resistance heating rod (Watlow Cartridge Heater,number E3A50) 2.5 mm from the microchannel array. Type 2 was a dual passexchanger containing 100 microchannels which were 2.5 mm×114 mm×0.25 mmand heated with a resistance heating rod (Watlow Cartridge Heater,number G6A6032) 2.5 mm from the microchannel array.

[0307] The combustion air was preheated to 160 to 170 C. using amicrochannel exchanger same as Type 2 exchanger described previously.

[0308] Combustion fuel was neat hydrogen to startup the device. Purehydrogen was selected as the startup fuel to avoid any coking potentialwithin the device, however it was anticipated that the device could alsobe started up with some amount of a hydrocarbon fuel in the mixture. Thefuel was not preheated externally to the device. Alternatively, the fuelcould have been preheated with either a microchannel exchanger or aconventional heat exchanger. The typical inlet fuel temperature asmeasured at the inlet to the ICR was 80 to 110 C. The temperature aboveambient is a result of gas heating via losses by line conduction fromthe hardware.

[0309] All inlet and outlet stream temperatures were measured using typeK thermocouples placed in the connecting tubes to the ICR reactor systemapproximately 5 to 10 cm from the inlet or outlet of the integrated heatexchanger on the ICR reactor system. Pressure transducers were added toeach of the inlet and outlet streams at similar locations.

[0310] The device was installed by connecting five Inconel 600 Swagelocktube fittings to the appropriate welded tube stubs on the ICR reactorsystem. The entire device installation time was less than an hour.

[0311] Thermocouples were installed on the outer surface of the ICRreactor system along the length of the exchanger portion and the reactorportion.

[0312] The required equipment included: the reactant feed Brooks 5850eand 5851e series mass flow controllers, Omega model FMA-A23 mass flowmeters, NoShok pressure transducers model 1001501127 and 1003001127,Omega latching relay controllers model CNI 1653-C24, Swagelok variablepressure relief valves, thermal conductivity detector gas chromatograph,NOVA model 300 CLD Chemiluminescent NO/NOx analyzer, etc. All equipmentwere calibrated and verified for proper operation. Flowrates werecalibrated against a primary standard calibrator, the Dry-Cal DC-2MPrimary Flow Calibrator, which was calibrated and certified by BIOSIntemational. Pressure transducers were calibrated using a Flukepressure calibrator model 718 1006 with a Fluke 700P07 or 700P06pressure module which were calibrated and certified by Fluke. The gaschromatograph and NO/NOx analyzer were calibrated against calibrationgases blended and certified by Praxair Distribution Inc.

[0313] The ICR reactor system was pressure tested by first applying astatic pressure to the SMR reactant line while plugging the SMR productline. The applied pressure was 217 psig and was generated using anitrogen fluid. The pressure was left on this side of the device.Concurrently, the combustion side was pressurized to 48 psig while theSMR side was under pressure. The combustion side pressure may not exceedthe SMR side pressure during pressure testing to maintain the mechanicalintegrity of the device. The leak rate did not exceed 0.5 psig in 15minutes, and then the ICR reactor system was ready for operation. Thecombustion catalyst was not reduced or treated prior to operation.

[0314] The SMR catalyst was reduced at about 120 to 150 C. The ICRreactor system was heated by using the integrated combustion portion ofthe reactor. This process was initiated by flowing nitrogen on the SMRside at 15.7 SLPM. This corresponds to a flowrate comparable to anequivalent contact time of 20 milliseconds during SMR catalystreduction. Nitrogen was then fed to the combustion side through theprimary air inlet at 12.0 SLPM and through the fuel inlet at 5.0 SLPM.Air was then blended with the nitrogen entering through the primary airline and fed at a rate of 0.51 sccm. The hydrogen was then started onthe fuel inlet at a flowrate of 0.11 sccm, which corresponds toapproximately 100% excess air. The hydrogen lit off at room temperature,and as soon as it did the fuel and air ratio was changed to achieve 5%excess air. The heat released from combustion heats the ICR reactorsystem. The heat up rate was roughly 5 C./minute.

[0315] Startup control was important for appropriate catalyst reductionto achieve a near isothermal (+/− 30 C.) temperature distribution alongthe length of the 7 inch catalyst section in the ICR reactor system.Control was achieved by varying the flowrates of the fuel hydrogen andair concurrently while keeping them at 5% excess air. Increases in thefuel hydrogen were offset by reductions in the fuel nitrogen, andincreases in the air flowrate were offset by reductions in the nitrogenflowing through the primary air line. This maintained a relativelyconstant flowrate to the combustion side of the ICR reactor system. Itwas important to maintain a roughly equal total flowrate of fluids inthe combustion side during startup to create a uniform temperatureprofile. If the combustion fluids flowrate drops by 50% or greater, thenthe front of the catalyst section becomes much hotter than the end ofthe catalyst section (+/−60 C. or higher). If the flowrate of thecombustion fluids increases by 50% or greater then the back end of thecatalyst section becomes much hotter than the front end of the catalystsection (+/− 60 C. or higher). In both scenarios, the catalyst does notproperly reduce.

[0316] The SMR catalyst was maintained at 120-150 C. (+/−20 C.) for onehour. During this hour, hydrogen at 10% of the nitrogen (1.57 SLPM H2and 15.7 SLPM N2) flowed by the SMR catalyst with a correspondingequivalent contact time of 18 milliseconds.

[0317] After the one-hour catalyst reduction process, the hydrogen onthe SMR process side was stopped. Nitrogen remains flowing on the SMRside at approximately 15.7 SLPM. The flowrate of nitrogen was roughlyequal to the total flowrate of SMR process reactants corresponding to an18 millisecond contact time. The 18 millisecond contact time was thefirst flowrate of process reactants and by setting the nitrogen flowrateto an equivalent value there was a lesser change in temperature profiledistribution in the ICR reactor system when the change occurs from purenitrogen during startup to operation of the ICR reactor system. Next theSMR side was pressurized to system operating pressure, 160 to 170 psigoutlet pressure, at 10-15 psig/min.

[0318] While nitrogen was flowing on the SMR side at a contact time of18 milliseconds, the combustion fluid flowrates were changed to heat thedevice to 600 C. Startup control was also critical for uniform heatingof the device and control of heating rate (not to excel 5 C./min asdescribed previously). Control was achieved by varying the flowrates ofthe hydrogen and air concurrently while keeping them at 1:2.5 ratiowhich corresponds to 5% excess air. Increases in the fuel and airflowrates were offset by reductions in the fuel nitrogen and primary airline nitrogen flowrates, respectively, to maintain a constant flowrateto the combustion side of the ICR reactor system. It was important tomaintain a roughly equal total flowrate of fluids in the combustion sideduring startup to create a uniform temperature profile and not exceed 5C./min.

[0319] To start the ICR combustion side heating, air was turned onthrough the primary air inlet line and hydrogen through the fuel inletline as described above while nitrogen also continues to flow into thesystem through the primary air inlet line and fuel inlet line. Theinitial flowrate of air and hydrogen were discussed previously. Thefluids were changed by increasing the air and hydrogen flowrates withina minute of each other while maintaining their ratio at 5% excess airand turning down both fuel and primary air line nitrogen to maintain aconstant overall flowrate. The constant overall flowrate roughlycorresponds to the total flowrate of combustion fuel and air required tooperate the SMR reaction at 18 ms at 600 C. By the time the devicereaches 600 C., the nitrogen will be reduced to zero.

[0320] If the air and hydrogen mixture did not light-off at roomtemperatures, then the microchannel exchanger system could be used toheat the ICR reactor system until light-off was obtained. Typically thecombustion side lights off at room temperature to 60C. After light-off,the microchannel exchanger system was set to maintain the inlettemperatures required for the ICR reactor system. Additionally, althoughair was not fed with fuel through the fuel inlet inline in this test,this could have been done to assist in combustion conversion.

[0321] When the SMR side reaches roughly 400 C., hydrogen was turned onthe SMR reactant side at 15% of the total flowrate of steamcorresponding to a 6:1 steam-to-carbon ratio at a contact time of 18milliseconds. This was roughly 2.5 SLPM. Within one minute, the waterpump on the SMR side was turned on to the liquid flowrate of 3 ml/min.Over the next 10 to 15 minutes, the liquid water flowrate was turned upin 3 m/min increments until the flowrate corresponded to a 6:1steam-to-carbon ratio at 18 milliseconds (12 ml/min). As the hydrogenand water feed rates increased, the nitrogen flowrate on the SMR sidewas correspondingly turned down to maintain the total stream at an 18 mscontact time.

[0322] The device continues to heat to 600 C. by changing the flowrateson the combustion side as described earlier. When the device reaches 600C., the combustion flows were slightly increased in preparation for theinitiation of the SMR reaction and corresponding heat sink. The flowswere increased to roughly 1.4 SLPM hydrogen through the fuel inlet line,and 3.51 SLPM air through the primary air inlet line. Within a minute,the SMR methane was turned on to match a 6:1 steam-to-carbon ratio at 18milliseconds. First the nitrogen and then the hydrogen on the SMR sidewere turned off and were not used again until shutdown of the ICRreactor system.

[0323] The initiation of SMR reaction created a heat load which requiredan increase in the combustion flowrates of hydrogen and air until thetemperature stabilized. Then device was then heated to the desiredoperating temperature for the reactor portion. As previously discussed,the primary air line nitrogen and fuel nitrogen were decreased as theprimary air line air and fuel hydrogen were increased, respectively,until the nitrogen to the primary air line and the fuel line were off.The steam-to-carbon and contact time were varied to the desiredexperimental conditions. As the steam-to-carbon and contact time werevaried, the heat load on the SMR side increases and the combustion sideflows were increased to maintain the desired reactor temperature. Theprocedure for turning up the combustion side flows was air then fuel,while turning down combustion side flows was fuel than air.

[0324] For the device, the temperature of the reactor portion of the ICRwas heated to at least 800 C. before reducing the steam-to-carbon to 3:1or below. During the transition from startup conditions to operatingconditions, the procedure for changing conditions on the SMR processside was to increase water flowrate before increasing SMR processhydrocarbon flowrate (i.e. going to a higher steam-to-carbon ratio thenback to the desired steam-to-carbon ratio).

[0325] Additionally, hydrocarbon feeds may be added to the combustionfuel during this time or earlier with a corresponding correction to theair flowrate to maintain proper fuel to air ratio. The procedure forthis process was to first increase the combustion primary air by theflowrate required to maintain the desired excess air ratio, then turn onthe hydrocarbon flowrate and then turn down the hydrogen flowrate by thesame energy output that the hydrocarbon flowrate was turned up.

[0326] The shutdown process was the reverse of the start-up process.

[0327] Emergency Shutdown

[0328] The ICR reactor systems has several interlocks which will turnoff the combustion and SMR process reactant flows if preset operatingtemperature or pressure high or low limitations were exceeded. If alimitation was exceeded, within milliseconds reactant flows were stoppedvia power-to-open valves and nitrogen was turned on at 3-5 SLPM to boththe SMR and combustion sides of the ICR reactor system. This flushes thedevice of all combustible fluids in less than 100 milliseconds, and willcontinue to flow until operator intervention resets the system.

[0329] Control Strategies

[0330] Several control strategies were implemented during the startup,operation and shutdown of the ICR reactor system.

[0331] First, during startup nitrogen and air were put into the primaryair inlet line, and nitrogen and fuel were put into the fuel inlet lineto better mimic the flow distribution when operating at full capacity.In this way the air and fuel could be distributed and mixed in a morefavorable way for the relatively small combustion flows required duringstartup. By making the startup mixture less flammable this procedurealso promoted a uniform catalytic combustion as opposed to homogeneouscombustion which could tend to concentrate the heat input to only smalllocalized regions. The temperature profile of the ICR reactor systemalong the 178 mm reactor length were controlled with total combustionflowrate (i.e. contact time) and stoichiometry (i.e. excess air). If thebeginning of the reaction zone was too cool, the flows were reduced (byreducing air and fuel together, or only reducing nitrogen whilemaintaining air and fuel flowrates constant) to decrease the temperaturenear the end of the reaction zone. Alternatively, if the end of the 178mm reaction zone was too cool, the flowrates were increased to createhigher temperatures in that area. The ratio of fuel to air was also usedto control the temperature profile of the ICR reactor system in thereaction zone without increasing or decreasing the total heat input.When the excess air was increased, the temperature maximum movedupstream, while a decrease in excess air (to as low as 3-5%) moved thetemperature maximum downstream.

[0332] Secondly, the air and fuel were varied in the manner describedpreviously to maintain temperature. This was achieved with a simplefeedback control loop. A thermocouple in the web area of the ICR reactorsystem was chosen as the control point. When the system got too cool,the feedback control increased the flowrate of air and fuel into the ICRreactor system while maintaining the desired ratio of fuel to air. Ifthe system got too warm, the feedback control operated in the reversemanner.

[0333] Thirdly, since changes in the ICR reactor system were typicallygradual over several hours, the use of preshutdown indicators/alarms wasvital to successful operation. These pre-shutdown indicators trigger at15-40% of the value of the interlocks, hence they warn operators well inadvance of a condition which would shutdown the system allowingoperators to react and control whatever parameter was moving out ofrange. This allows the ICR reactor system to be operated withoutconstant supervision, but still be able to be corrected should thesystem drift out of specification.

[0334] Fourth, the use of nitrogen during startup to imitate the totalflowrate entering the SMR process side reduces the temperature shockmagnitude as the SMR reactants were turned on and the SMR nitrogen wasturned off. This was important as the small size of the ICR reactorsystem and its quick response due to the microchannel architecture makeit susceptible to sudden and potentially harmful temperature changes.

[0335] Fifth, when combustion flows were increased the air was turned upbefore the fuel to prevent entering a fuel rich regime momentarily inwhich the combustion chemistry could change and alter the temperatureprofile along the ICR reactor system.

[0336] Sixth, when SMR process side flows were increased the change wasalways made such that a higher steam-to-carbon ratio was achieved priorto the endpoint steam-to-carbon ratio. For example, if both water andhydrocarbon were to be increased, then the water was increased first andthe hydrocarbon secondly.

[0337] Results

[0338] The reactor operated over 300 hours, continuously producingequilibrium SMR products at an apparent equilibrium temperature of about865 C. During the 300 hours of operation, a 9 ms SMR contact time, ˜12bar outlet pressure, and a steam-to-carbon ratio of 2.5 to 1 wasmaintained. During the first 50 hours of operation 5% excess combustionair was used, after which 10% excess air was used. More than 70 hours ofthe bonded ICR continuous operation were carried out with 10% methane inthe combustion fuel feed. During the demonstration, little or no losswas observed in either SMR or combustion activity.

[0339] Detailed data from the testing can be found in Table 1. After theinitial 25 hours, complete combustion was observed with 5-10% methane inthe combustion fuel. The SMR reaction absorbed nearly 75% of the heatprovided by the combustion reaction. CO and NOx concentrations in thedry combustion effluent were less than 0.1% and 8 ppm, respectively. InTable 1, average reactor temperatures were assumed to be the average ofthe three skin temperature measurements closest to the U-turn on oneface, spanning the last quarter of the reaction zone. Skin temperaturesreported in Table 1 were measured along the centerline of one face,tracking the edge nearest the middle combustion exhaust channel. SMRcontact time was calculated based on the entire volume of the six SMRreaction channels, including catalyst, spacers, and flow-by gap adjacentto the catalyst. The dimensions of each SMR reaction channel were 17.78cm long by 0.965 cm wide by 0.051 cm tall, for a total volume of 5.23cm³ (including all six channels). Some error was found to be associatedwith dry product exit flow measurements due to changes in the dry testmeter calibration, thought to be due to water accumulation in the testmeter. This, combined with minor errors in mass flow controller and GCcalibrations, contributed to carbon balance errors in the range of ±15%.

[0340] Results during the 300 hours of operation of the device are shownin graphical form in FIGS. 25 to 27. Despite a few process upsets causedby balance of plant issues, the device performance was remarkably steadythroughout the entire 300 hours of operation (see FIG. 25).

[0341] Device temperatures (see FIG. 26) were also quite steady duringoperation, although a pattern of cyclic behavior is seen in thetemperatures which cycled with daily changes in the ambient temperature.

[0342]FIG. 27 shows the combustion performance. Note that during thefirst 25 hours of operation, the methane combustion conversion steadilyimproved until complete combustion was achieved. The dry exhaust showedno detectable CO until the methane concentration in the fuel stream wasincreased to 10% (about 225 hours on stream), at which point the COconcentration in the dry exhaust was <0.1%. The total combustion heat ofreaction was the same for both the 5% and the 10% methane combustionfuel conditions, resulting in nearly identical average skin temperaturesand SMR performance both before and after the change. TABLE 1 Selectedresults from operation of the bonded ICR device of Example 1. 50 hour225 hour Initial 5% excess 10% XS performance air air 10% CH4 Time onstream (hours) 1.5 46.5 225 298 Air inlet gas temperature 163 162 164164 (° C.) Fuel inlet gas temperature 81 81 84 84 (° C.) Exhaust gastemperature 330 332 343 347 (° C.) Air inlet pressure (Pa/10⁵) 2.12 2.132.21 2.25 Fuel inlet pressure (Pa/10⁵) 2.30 2.31 2.43 2.50 Exhaustoutlet pressure 1.46 1.46 1.50 1.54 (Pa/10⁵) Total fuel flow rate (SLPM)10.1 10.1 10.1 9.4 Fuel H₂ content (%) 89 89 89 81.3 Fuel CH₄ content(%) 5 5 5 9.7 Fuel CO₂ content (%) 6 6 6 9 Air flow rate (SLPM) 27.527.6 28.9 29.7 % excess air (based on inlet) 5 5 10 10 % excess air(measured) 12.9 12.8 25.0 27.5 Combustion contact time 9.1 9.1 8.8 8.8(ms)^(a) Air pressure drop (Pa/10⁵) 0.66 0.67 0.72 0.72 Fuel pressuredrop (Pa/10⁵) 0.84 0.85 0.93 0.97 Combustion H₂ conversion 100 100 100100 (%) Combustion CH₄ conversion 93.5 100 100 100 (%) Comb. selectivityto CO₂ 100 100 100 100 (%) Comb. (carbon out)/(carbon 0.49 0.50 0.620.67 in) Combustion exhaust NOx not meas. not meas. not meas. 7 (ppm)SMR inlet gas temperature 278 284 284 282 (° C.) SMR outlet gastemperature 317 324 326 326 (° C.) SMR inlet pressure (Pa/10⁵) 13.4915.90 17.97 18.04 SMR outlet pressure (Pa/10⁵) 12.32 12.39 12.18 12.25SMR average pressure 12.9 14.1 15.1 15.1 (Pa/10⁵) SMR pressure drop(Pa/10⁵) 1.2 3.5 5.8 5.8 SMR to comb. differential 11.0 12.3 13.1 13.1(Pa/10⁵) SMR CH₄ flow rate (SLPM) 9.96 9.96 9.96 9.96 SMR steam flowrate 25.1 25.1 25.1 25.1 (SLPM) Molar Steam to Methane 2.5 2.5 2.5 2.5Ratio SMR contact time (ms) 9.0 9.0 9.0 9.0 CH₄ conversion (GC Basis)89.3 90.8 88.9 89.2 (%) Selectivity: CO (%) 72.9 73.4 74.9 74.4 SMR(carbon out)/(carbon 0.92 0.93 0.86 0.86 in) Average reactor skin temp.876 901 902 905 (° C.)^(b) Equilibrium conversion T 863 873 860 862 (°C.) Equilibrium selectivity T 881 887 ˜900 898 (° C.) SMR rxn.heat/comb. rxn. 0.740 0.746 0.733 0.734 Heat^(c) Average area heat flux14.0 14.2 14.0 14.0 (W/cm²) Reactor core volumetric flux 64.7 65.9 64.664.8 (W/cm³) Endothermic reaction 275 280 275 275 chamber flux (W/cm³)Skin temperature at u-turn (° C.) 846 870 870 875 Skin temperature 25.4mm from u- 886 912 912 916 turn (° C.) Skin temperature 50 8 mm from u-896 920 923 924 turn (° C.) Skin temperature 76 mm from u- 892 913 568568 turn (° C.) Skin temperature 102 mm from u- 876 894 915 917 turn (°C.) Skin temperature 127 mm from u- 852 866 897 901 turn (° C.) Skintemperature 152 mm from u- 828 844 880 872 turn (° C.) Skin temperature178 mm from u- 793 794 826 807 turn (° C.) Skin temperature 197 mm fromu- 727 731 750 747 turn (° C.) Skin temperature 216 mm from u- 686 691713 705 turn (° C.) Skin temperature 254 mm from u- 629 635 656 651 turn(° C.) Skin temperature 343 mm from u- 487 492 506 504 turn (° C.) Skintemperature 431 mm from u- 352 357 363 363 turn (° C.)

[0343] The average reactor temperature was calculated as the average ofthe perimeter metal or metal web thermocouple measurements made alongthe last 25-30% of the reactor (furthest downstream).

[0344] Over 300 hours of operation, the SMR reactant inlet pressureincreased from 180 psig to about 245 psig while the SMR product outletpressure was maintained at about 165 psig. SMR methane flow rate wasmaintained at 10 SLPM. SMR liquid water flow rate was maintained at 20cc liquid per minute. The temperature of the SMR reactant inlet gastemperature was maintained at about 283 C. and the SMR outlet gastemperature maintained at about 325 C. throughout operation.

[0345] These results are superior to any prior art device that would beoperated at the same contact time.

[0346] For the first 50 hours, the bonded ICR was operated with 5%excess air (by volume) for combustion, then 10% excess air for the next250 hours. For the first 225 hours of operation the fuel contained 5%methane, 89% hydrogen and 6% CO₂, and then changed to 10% methane, 81%hydrogen and 9% CO₂ for the next 75 hours of operation. Throughoutoperation, the air inlet temperature was about 160 C., the fuel inlettemperature was about 80 C., and the exhaust gas temperature was about330 C. for the first 50 hours, increasing to about 343 C. for the next175 hours and then increasing to about 347 C. for the last 75 hours.

Example 2

[0347] Bonded Device; Results and Discussion

[0348] The bonded ICR device of Example 2 was demonstrated using methaneand steam at 2.5:1 steam:C, 850 C. and 12.5 atm. Testing included 88hours at 6 ms followed by >300 hours at 9 ms. Combustion fuelcomposition was 5-10% CH₄, 0-2% CO, 6% CO₂, and the balance H₂. Excesscombustion air was maintained between 3 and 7%.

[0349] Results of the testing are shown in Table 2 and FIGS. 28-31. InTable 2, average reactor temperatures were assumed to be the average ofthe three skin temperature measurements closest to the U-turn on oneface, spanning the last quarter of the reaction zone. Skin temperaturesreported in Table 2 were measured along the centerline of one face,tracking the edge nearest the middle combustion exhaust channel. FIG. 28shows the SMR performance over the entire 400 hours of operation. InFIG. 29, combustion results are shown from the bonded ICR testing. Onesurprising result shown in FIG. 29 is combustion CH₄ conversions whichexceed the H₂ conversion. Another is the increase in CO and decrease inH₂ conversion when the reactor is heated to above 950 C. One explanationfor these observations is that the methane combustion does not go tocompletion in the combustion zone at these high combustion flow rates,partially oxidizing to hydrogen and carbon monoxide somewhere in theexhaust channel. FIG. 30 shows how measured skin temperatures along thereactor length varied during operation. FIG. 31 shows SMR performanceover a range of SMR contact times for a steam-to-carbon ratio of 3.0.TABLE 2 Selected results from operation of the bonded ICR device ofExample 2. Contact Time 6 ms 9 ms Time on stream (hours) 35 131 Airinlet gas temperature (° C.) 161 158 Fuel inlet gas temperature (° C.)91 102 Exhaust gas temperature (° C.) 352 306 Air inlet pressure(Pa/10⁵) 2.38 1.99 Fuel inlet pressure (Pa/10⁵) 2.54 2.09 Exhaust outletpressure (Pa/10⁵) 1.67 1.47 Total fuel flow rate (SLPM) 14.4 9.76 FuelH₂ content (%) 87.0 87.0 Fuel CH₄ content (%) 5.0 5.0 Fuel CO₂ content(%) 2.0 2.0 Fuel CO content (%) 6.0 6.0 Air flow rate (SLPM) 38.4 27.0 %excess air (based on inlet) 3 7 % excess air (measured) 6 11 Combustioncontact time (ms)^(a) 6.3 9.0 Air pressure drop (Pa/10⁵) 0.71 0.52 Fuelpressure drop (Pa/10⁵) 0.86 0.62 Combustion H₂ conversion (%) 94.0 94.8Combustion CH₄ conversion (%) 98.8 98.4 Comb. selectivity to CO₂ (%)84.2 84.1 Comb. (carbon out)/(carbon in) 0.79 0.78 Combustion exhaustNOx (ppm) 3.4 2.8 SMR inlet gas temperature (° C.) 280 269 SMR outletgas temperature (° C.) 334 307 SMR inlet pressure (Pa/10⁵) 13.14 13.08SMR outlet pressure (Pa/10⁵) 11.84 12.25 SMR average pressure (Pa/10⁵)12.5 12.7 SMR pressure drop (Pa/10⁵) 1.3 0.8 SMR to comb. differential(Pa/10⁵) 10.4 10.9 SMR CH₄ flow rate (SLPM) 14.94 9.96 SMR steam flowrate (SLPM) 37.52 25.06 Molar Steam to Methane Ratio 2.5 2.5 SMR contacttime (ms) 6.0 9.0 CH₄ conversion (GC Basis) (%) 86.8 87.3 Selectivity:CO (%) 69.5 72.1 SMR (carbon out)/(carbon in) 0.93 0.97 Average reactorskin temp. (° C.)^(b) 893 875 Equilibrium conversion T (° C.) 840 840Equilibrium selectivity T (° C.) 840 870 SMR rxn. heat/comb. rxn.heat^(c) 0.81 0.80 Average area heat flux (W/cm²) 20.3 13.6 Reactor corevolumetric flux (W/cm³) 76.0 51.1 Endothermic reaction chamber flux 323217 (W/cm³) Skin temperature at u-turn (° C.) 872 853 Skin temperature25.4 mm from u-turn (° C.) 900 881 Skin temperature 50.8 mm from u-turn(° C.) 908 891 Skin temperature 76 mm from u-turn (° C.) 906 899 Skintemperature 102 mm from u-turn (° C.) 899 883 Skin temperature 127 mmfrom u-turn (° C.) 585 573 Skin temperature 152 mm from u-turn (° C.)862 845 Skin temperature 178 mm from u-turn (° C.) 562 781 Skintemperature 197 mm from u-turn (° C.) 763 749 Skin temperature 216 mmfrom u-turn (° C.) 714 702 Skin temperature 254 mm from u-turn (° C.)638 624 Skin temperature 343 mm from u-turn (° C.) 511 499 Skintemperature 431 mm from u-turn (° C.) 390 362

[0350] As can be seen from the data in FIG. 31, there was essentially nochange in results caused by varying contact time between 6 and 18 ms.

[0351] Welded ICR-N2

[0352] Installation/Startup

[0353] The microchannel ICR reactor system contains a series ofintegrated exchangers to preheat the process reactant, combustion airand combustion fuel. The integrated exchanger also cools the processproduct and combustion exhaust. The steams entering the device mayeither be at ambient conditions or at a slightly elevated temperature. Aseries of microchannel exchangers were optionally used to provideadditional preheat to the streams. Additionally, the reactor portion ofthe ICR reactor system was surrounded by a conventional half-shellceramic heater. This device was also used to provide heat, but to thereactor portion and was mounted ½ inch to ¾ inch from the exteriorsurface of the ICR reactor system.

[0354] The process reactant was preheated to 280 to 310 C. using themicrochannel exchanger system described above. The combustion air waspreheated to 150 to 160 C. using a microchannel exchanger same as Type 2exchanger described previously.

[0355] Combustion fuel was neat hydrogen to startup the device. Purehydrogen was selected as the startup fuel to avoid any coking potentialwithin the device, however it was anticipated that the device could alsobe started up with some amount of a hydrocarbon fuel in the mixture. Thefuel was not preheated externally to the device. Alternatively, the fuelcould have been preheated with either a microchannel exchanger or aconventional heat exchanger. The typical inlet fuel temperature asmeasured at the inlet to the microchannel ICR reactor system was 110 to120C.

[0356] All inlet and outlet stream temperatures were measured using typeK thermocouples placed in the connecting tubes to the ICR reactor systemapproximately 5 to 10 cm from the inlet or outlet of the integrated heatexchanger on the ICR reactor system. Pressure transducers were added toeach of the inlet and outlet streams at similar locations.

[0357] The device was installed by connecting five Inconel 600 Swagelocktube fittings to the appropriate welded tube stubs on the ICR reactorsystem. The entire installation time was less than an hour.

[0358] Thermocouples were installed on the outer surface of the ICRreactor system along the length of the exchanger portion and the reactorportion.

[0359] The system equipment included: reactant feed Brooks 5850e and5851e series mass flow controllers, Omega model FMA-A23 mass flowmeters, NoShok pressure transducers model 1001501127 and 1003001127,Omega latching relay controllers model CNI 1653-C24, Swagelok variablepressure relief valves, thermal conductivity detector gas chromatograph,NOVA model 300 CLD Chemiluminescent NO/NOx analyzer, etc. The equipmentwere calibrated and verified for proper operation. Flowrates werecalibrated against a primary standard calibrator, the Dry-Cal DC-2MPrimary Flow Calibrator, which was calibrated and certified by BIOSInternational. Pressure transducers were calibrated using a Flukepressure calibrator model 718 1006 with a Fluke 700P07 or 700P06pressure module which were calibrated and certified by Fluke. The gaschromatograph and NO/NOx analyzer were calibrated against calibrationgases blended and certified by Praxair Distribution Inc.

[0360] The ICR reactor system was pressure tested by first applying astatic pressure to the SMR reactant line while plugging the SMR productline. The applied pressure was 205 psig and was generated using anitrogen fluid. The pressure was left on this side of the device.Concurrently, the combustion side was pressurized to 55 psig while theSMR side was under pressure. The combustion side pressure may not exceedthe SMR side pressure during pressure testing to maintain the mechanicalintegrity of the device. The leak rate did not exceed 0.5 psig in 15minutes, and the ICR reactor system was ready for operation.

[0361] The combustion catalyst was reduced for one hour at roomtemperature with 1 SLPM hydrogen (55 millisecond contact time), noexternal heat was provided. The combustion fluids were then initiated inthe following manner to achieve proper temperatures for SMR catalystreduction. The SMR catalyst reduction temperature was 250 to 300 C. TheICR reactor system was preheated by using the integrated combustionportion of the reactor. The process was initiated by increasing thenitrogen flowrate on the SMR side to 2.5 SLPM. This corresponds to acontact time of 21 milliseconds. The hydrogen was then turned off on thecombustion side fuel inlet. Nitrogen was then fed to the combustion sidethrough the primary air inlet at 2.0 SLPM, and the fuel inlet at 1.0SLPM. The air was then blended with the nitrogen and fed at a rate of0.5 SLPM. Then the hydrogen was restarted on the combustion side fuelinlet at a flowrate of 200 sccm. The hydrogen lit off at roomtemperature. The heat released from combustion heats the ICR reactorsystem. The heat up rate was roughly 5 C./minute.

[0362] Startup control was important for appropriate catalyst reductionto achieve a near isothermal (+/−30 C.) temperature distribution alongthe length of the 7 inch (178 mm) catalyst section in the ICR reactorsystem. Control was achieved by varying the flowrates of the hydrogenand air concurrently while keeping them at specified ratio whichcorresponds to 5% excess air. Increases in the fuel and air flowrateswere offset by reductions in the fuel and primary air line nitrogenflowrates, respectively, to maintain a constant flowrate to thecombustion side of the ICR reactor system. It was important to maintaina roughly equal total flowrate of fluids in the combustion side duringstartup to create a uniform temperature profile. If the combustionfluids flowrate drops by 50% or greater, then the front of the catalystsection becomes much hotter than the end of the catalyst section (+/−60C. or higher). If the flowrate of the combustion fluids increases by 50%or greater then the back end of the catalyst section becomes much hotterthan the front end of the catalyst section (+/−60 C. or higher). In bothscenarios, the catalyst does not properly reduce. Once the temperatureof the ICR reactor system reached 250 to 300 C. in the reaction zone,the SMR hydrogen flowrate was gradually stepped in over one hour to 10%of the SMR nitrogen flowrate. After one hour, the SMR hydrogen was at0.25 SLPM which corresponds to a contact time of 19 milliseconds and theone hour reduction time began.

[0363] The SMR catalyst was maintained at 250 to 300 C. (+/−20 C.) forone hour. During this hour, hydrogen at 10% of the nitrogen (0.25 SLPMH2 and 2.5 SLPM N2) flow by the SMR catalyst with a correspondingcontact time of 19 milliseconds.

[0364] After the one-hour catalyst reduction process, the hydrogen onthe SMR process side was stopped. Nitrogen remains flowing on the SMRside at approximately 2.5 SLPM. The flowrate of nitrogen was roughlyequal to the total flowrate of SMR process reactants corresponding to an18 millisecond contact time. The 18 millisecond contact time was thefirst flowrate of process reactants and by setting the nitrogen flowrateto an equivalent value there was a lesser change in temperature profiledistribution in the ICR reactor system when the change occurs from purenitrogen during startup to operation of the ICR reactor system.

[0365] Next the SMR side was pressurized to system operating pressure,175 to 185 psig outlet pressure, at 10-15 psig/min. While nitrogen wasflowing on the SMR side at a contact time of 18 milliseconds, thecombustion fluid flowrates were changed to heat the device to 600 C.Startup control was also important for uniform heating of the device andcontrol of heating rate (not to exceed 5 C./min as describedpreviously). Control was achieved by varying the flowrates of thehydrogen and air concurrently while keeping them at 1:2.5 ratio whichcorresponds to 5% excess air. Increases in the fuel and air flowrateswere offset by reductions in the fuel nitrogen and primary air linenitrogen flowrates, respectively, to maintain a constant flowrate to thecombustion side of the ICR reactor system.

[0366] To start the ICR combustion side heating, air was turned onthrough the primary air inlet line and hydrogen through the fuel inletline while nitrogen also continues to flow into the system through theprimary air inlet line and fuel inlet line. The initial flowrate of airand hydrogen was discussed previously. The fluids were changed byincreasing the air and hydrogen flowrates within a minute of each otherwhile maintaining their ratio at 5% excess air and turning down bothfuel and primary air line nitrogen to maintain a constant overallflowrate. The constant overall flowrate roughly corresponds to the totalflowrate of combustion fuel and air required to operate the SMR reactionat 18 ms at 600 C. By the time the device reaches 600 C., the nitrogenwas be reduced to zero.

[0367] If the air and hydrogen mixture did not light-off at roomtemperatures, then the microchannel exchanger system could be used toheat the ICR reactor system until light-off was obtained. Typically thecombustion side lights off at room temperature to 60C. After light-off,the microchannel exchanger system was set to maintain the inlettemperatures required for the ICR reactor system. Additionally, althoughair was not fed with fuel through the fuel inlet inline in this test,this could have been done to assist in combustion conversion.

[0368] When the SMR side reaches roughly 400 C., hydrogen was turned onthe SMR reactant side at 15% of the total flowrate of steamcorresponding to a 6:1 steam-to-carbon ratio at 18 milliseconds. Thiswas roughly 380 sccm. Within one minute, the water pump on the SMR sidewas turned on to the liquid flowrate of 2 ml/min (corresponding to theinitial process condition of 6:1 steam-to-carbon ratio at 18milliseconds). As the hydrogen and water feed rates were increased, thenitrogen flowrate on the SMR side was correspondingly turned down tomaintain the total stream at an 18 ms contact time.

[0369] The device continued to heat to 600 C. by changing the flowrateson the combustion side as described previously. When the device reached600 C., the POx catalyst required reduction. This was achieved by simplymaintaining the POx region of the ICR reactor system at the required600C. With the feed of pure hydrogen, the catalyst was reduced as theair joined with the hydrogen downstream of the POx catalyst andcombusted to provide the heat for reduction but did not interfere withreduction.

[0370] Then the SMR reaction was initiated by the following sequence ofevents which were all completed within one minute: the SMR methane wasturned on to match a 6:1 steam-to-carbon ratio at 18 milliseconds, thenthe nitrogen and then the hydrogen on the SMR side were turned off andwere not be used again until shutdown of the ICR reactor system.

[0371] The initiation of the SMR reaction caused the ICR reactor systemto cool, so the combustion flows were increased until the temperaturestabilized at 600 C. (+40C., −0C.) in the reactor portion of the ICRreactor system. During this time the nitrogen on the combustion sidethrough the primary air inlet line and the fuel line were turned off.The device was then heated to 860C. at which point the steam-to-carbonratio was changed to 3:1 and the contact time to 12 milliseconds. Theflowrates of air through the primary air line and fuel through the fuelline were changed to maintain temperature. Then the externally mountedceramic heater was employed to maintain the ICR reactor system at 860C.while the hydrogen fuel was turned down gradually until it was off. Thenhydrocarbon and air were fed through the fuel inlet to the combustionside. While maintaining a hydrocarbon to oxygen ratio of 2:1, theseflows were increased until the ceramic heater was no longer needed toprovide heat to maintain temperature at which point the ceramic heaterwas turned off.

[0372] The combustion side flows were now altered to maintain thedesired operating temperature for the reactor portion. Thesteam-to-carbon and contact time were varied to the desired experimentalconditions. As the steam-to-carbon and contact time were varied, theheat load on the SMR side increases and the combustion side flows wereincreased to maintain the desired reactor temperature. The procedure forturning up the combustion side flows was to first increase thecombustion primary air by the flowrate required to maintain the desiredexcess air ratio, and then turn up the hydrocarbon flowrate and fuel airin the same ratio.

[0373] For the device, the temperature of the reactor portion of the ICRwas heated to at least 800 C. before reducing the steam-to-carbon to 3:1or below as proscribed by the desired run plan. During the transitionfrom startup conditions to operating conditions, the procedure forchanging conditions on the SMR process side was to increase waterflowrate before increasing SMR process hydrocarbon flowrate (i.e. goingto a higher steam-to-carbon ratio then back to the desiredsteam-to-carbon ratio).

[0374] Shut Down

[0375] The shutdown process was the inverse of the start-up process.Emergency shutdown procedures were the same as discussed previously.

[0376] Control Strategies

[0377] Several control strategies were implemented during the startup,operation and shutdown of the ICR reactor system. The first three ofthese control strategies are the same as discussed previously.

[0378] Fourth, the use of nitrogen during startup to imitate the totalflowrate entering the SMR process side reduces the temperature shockmagnitude as the SMR reactants were turned on and the SMR nitrogen wasturned off. This was important as the small size of the ICR reactorsystem and its quick response due to the microchannel architecture makeit susceptible to sudden and potentially harmful temperature changes.

[0379] Fifth, when combustion side flows were increased the air wasturned up before the fuel to prevent entering a fuel rich regimemomentarily in which the combustion chemistry could change and alter thetemperature profile along the ICR reactor system.

[0380] Sixth, when SMR process side flows were increased the change wasalways made such that a higher steam-to-carbon ratio was achieved priorto the endpoint steam-to-carbon ratio. For example, if both water andhydrocarbon were to be increased, then the water was increased first andthe hydrocarbon secondly.

[0381] Seventh, the use of the external ceramic heater surrounding thereactor portion of the ICR reactor system allowed the device to bestarted up on pure hydrogen as the combustion fuel and then safely andefficiently changed over to hydrocarbon fuel feed. This circumvented theneed to enter into a potentially explosive region of hydrogen or methanein air concentrations prior to their entrance into the combustion regionof the ICR reactor system.

[0382] Welded ICR N3

[0383] Installation/Startup

[0384] The installation and operation of N3 follows the same procedureas N2 with the following exceptions:

[0385] 1. The system was pressure tested at 290 psig on the SMR processside and 70 psig on the combustion side.

[0386] 2. The SMR process inlet was preheated to 280 to 340 C.

[0387] 3. The combustion side primary air inlet was preheated to 140 to160 C.

[0388] 4. The combustion side fuel inlet was preheated to 50 to 70 C.

[0389] 5. Although the methodology was similar for N3 as N2, theflowrates used for initial light-off were different. Nitrogen was fed tothe combustion side through the primary air inlet at 3.0 SLPM, while thefuel nitrogen was off. The fuel hydrogen was at 200 sccm and the primaryair was 4.0 SLPM, which corresponds to 750% excess air. Light-offoccurred at 200C., and the heatup time was reduced by the use of theceramic shell heater. Following light-off, N3 continued to be started upin the same manner as N2.

[0390] 6. N3 did not contain a POx section of the ICR reactor system,consequently the POx section was not reduced. Rather when the devicereached 600C., the SMR reaction was then initiated as discussed in theN2 example.

[0391] 7. The operating pressure was 185 to 195 psig at the SMR processside outlet.

[0392] 8. When the ICR reactor system reached 600C., the SMR reactionwas initiated at 4.5:1 steam-to-carbon ratio and 18 milliseconds.

[0393] Control Strategies

[0394] The control strategies of N3 follow the same procedures asdescribed for welded ICR N2 with the following exceptions:

[0395] 1. Excess air was employed as a variable to obtain combustionside light-off of hydrogen.

[0396] Although typically 5% excess air was used during hydrogenlight-off, this variable was changed to 750% to achieve light-off forN3.

[0397] Results

[0398] The co-flow pattern was arranged between two combustion channelsand one reformer channel. A flow-by design was made in reformer channelto provide low pressure drop by allowing the reactant stream in thechannel to flow in a narrow gap (about 0.2 mm) between solid channelwall and a layer of porous engineered catalyst which is in intimatethermal contact with the heat transfer surface (solid metal betweencombustion and reformer channels. Two different designs were used incombustion channel, one was for methane direct combustion and the otherwas for partial oxidation of methane followed by methane, carbonmonoxide and hydrogen combustion. A U-turn was designed to connectcombustion exhaust channels and reformer product channel with combustionfuel and air channels and reformer reactant channel respectively. Arecuperator was integrated directly with reactor to balance heatdistribution between five streams, which include reformer reactant,product, combustion air, fuel and exhaust flow. Both the reformer andcombustion streams follow a loop flow pattern. The reformer reactantcomes up the outer side of the loop, which had porous engineeringcatalyst on one side of the solid channel wall, and returned in theadjacent product channel, where there was no catalyst. The combustionfuel entered the outer sides of the second M, where air was jetted intothe combustion channel from air channel, which was between fuel channeland exhaust channel, and heat was transferred to the adjacent reformerreactant channel. The exhaust stream exits the center of the second M.This integrated device was the combination of two halves of two adjacenttwo-stream loops. This integrated reactor test results demonstrated thatthe concept can be scaled up for commercial application.

[0399] Start up 1

[0400] After the reactor was stabilized at 850° C., an external ceramicheater was turned on to maintain reactor temperature while combustionhydrogen was turn down gradually till it was shut off. Methane wasintroduced to combustion fuel channel and ramp up gradually whileexternal ceramic heater was turned down gradually to maintain reactortemperature. After the reactor steady state was established when ceramicheater was turned off, both reformer and combustion sides can beadjusted to target conditions.

[0401] Start up 2

[0402] After POx catalyst was reduced at 600° C. for 1 hour, combustionhydrogen was shut off to drop the reactor temperature to 400° C. andthen an external ceramic heater was turned on to maintain the reactortemperature. As the reactor temperature was 400° C., combustion fuel andair were introduced to combustion channel to heat up reactor to 600° C.Ceramic heater was shut off during the heating up. After both reformerand combustion sides were stabilized at 600° C., water and hydrogen (15%of vapor volume) were introduced to reformer side while maintaininginert flow. Once water flow was established, methane was turned on,while hydrogen and inert was shut off, to maintain at 6:1steam-to-carbon ratio and 18 ms contact time in reformer side. Then thereformer side was heated up to 850° C. by increasing hydrogen and airflow rate in combustion side. Then water and methane flow in reformerside can be adjusted to target conditions by maintaining constantreactor temperature, which can be accomplished by adjusting combustionfuel and air flow.

[0403] Results and Discussion for Welded ICR N2 and N3

Example

[0404] Welded ICR-N2 was designed to test the effectiveness of partialoxidation of methane (POx) and then combustion of methane. This was doneby solution coating 100 ppi metal foam with POx catalyst. N2 operatedfor a total of 606 hours and these results are shown in Tables 3 and 4.For roughly 40 hours of this test, natural gas was used on both theprocess and combustion side without change in performance. In generalthe design had good performance with POx followed by combustion.

[0405] N2 also successfully demonstrated a simplified start-upprocedure. Devices can be heated with hydrogen initially to preheat thedevice (or alternatively the device can be heated with an externalheater). During the switch from a hydrogen fuel in the fuel line to aPOx fuel mixture in a safe manner, the device is anticipated to cool. Itis anticipated that the device will not cool to below 400 C. Thisstart-up procedure was tested by heating the reactor to between 375 and400° C and initiating the POx feed. There were no problems heating withthis method as the POx catalyst lit off extremely well. The entirestart-up procedure after initiation of the POx feed was remarkablysimilar to starting the SMR on pure hydrogen. This test was repeatedtwice and the same results were observed. TABLE 3 Welded ICR N2 (POxassisted combustion) results Air inlet gas temperature (° C.) 160 152153 151 fuel inlet gas temperature (° C.) 160 160 157 153 Exhaust gastemperature (° C.) 357 353 356 355 Air inlet gas pressure (psig) 26.0625.05 26.37 26.16 Total fuel flow rate (SLPM) 1.2 CH4 1.18 CH4 1.2 CH41.2 NG Fuel H2 content (%) 0 0 0 0 Fuel CH4 or NG content (%) 100% CH4100% CH4 100% CH4 100% NG Air channel flow rate (SLPM) 11.5 11.32 11.511.5 POx premixed air flow rate (SLPM) 2.86 2.81 2.97 2.97 Fuel to O2ratio of POx 2 2 1.95 1.95 % excess air 25 25 25 25 ICR contact time(ms) 4.3 4.4 4.3 4.3 Air pressure drop (psi) 18.74 17.74 18.65 19.03Fuel pressure drop (psi) 93.70 91.79 91.76 95.91 Combustion H2conversion (%) Na Na Na Na Combustion CH4 conversion (%) 96.2 92.1 98.395.5 Comb. Selectivity to CO (%) 5.2 2.0 11.5 6.2 Combustion exhaust NOx(ppm) 5.2 Na Na Na Combustion CO exhaust (ppm) 3820 1403 8545 4542Thermo loss (W)* 389.1 395.8 365.7 365.0 SMR heat duty (W)^(c) 303.9295.5 310.6 311.5 Combustion heat duty (W)^(d) 699.7 697.8 679.8 662.6SMR heat duty/combustion heat duty 0.43 0.42 0.46 0.47 SMR inlet gastemperature (° C.) 306 305 303 301 SMR outlet gas temperature (° C.) 339337 322 322 SMR inlet pressure (psig) 201.3 200.6 198.4 197.11 SMRoutlet pressure (psig) 168.1 167.9 176.7 174.89 Pressure gradientbetween SMR 130.99 131.33 134.74 131.38 channel and fuel channel (Psi)SMR CH4 or NG flow rate (SLPM) 2.08 CH4 2.08 CH4 2.18 CH4 2.13 NG SMRsteam flow rate (CCM) 8.04 8.04 5.30 5.44 Molar steam-to-carbon ratio4.8 4.8 3.03 3.07 SMR contact time (ms) 4.3 4.3 6.0 5.9 SMR CH4conversion (GC Basis) 93.4 91.3 89.2 91.7 (%) SMR Selectivity: CO (%)51.7 49.8 65.1 64.1 Average web temperature (° C.) 868 840 875 881Equilibrium conversion temperature 811 795 847.3 863.4 (° C.)Equilibrium selectivity temperature 846 828 856.7 847.9 (° C.) SMRpressure drop (psi) 33.2 32.7 22.73 22.22 Average heat flux (W/cm2) 17.717.2 18.1 18.2 Average reactor core volumetric flux 66.4 64.6 67.9 68.1(W/cm3)^(ae) Endothermic Chamber heat flux 278.8 271.1 285 285.8(W/cm3)^(f) Time on Stream (Hr) 277 278 565 576

[0406] TABLE 4 Temperature profile of N2 Location 1 2 3 4 SMR reactantCH4 CH4 CH4 NG SMR S:C 4.8 4.8 3 3 SMR CT 4.3 4.3 6 6 ICR fuel CH4 CH4CH4 NG ICR CH4 conversion/% 96.2 92.1 98.3 97.7 TC22(2″ above SMR zone)° C. 789 780 799 798 TC23(0.5″ above SMR zone) ° C. 778 768 779 780TC24(0.18″ of 7″ SMR zone) ° C. 857 844 857 855 TC25(0.79″ of 7″ SMRzone) ° C. 836 823 836 838 TC27(2.25″ of 7″ SMR zone) ° C. 847 827 837837 TC28(2.97″ of 7″ SMR zone) ° C. 848 825 848 850 TC29(3.57″ of 7″ SMRzone) ° C. 849 825 849 854 TC31(4.94″ of 7″ SMR zone) ° C. 865 838 870875 TC32(6.34″ of 7″ SMR zone) ° C. 877 848 884 891 TC47(0.02″ below SMRzone) ° C. 862 833 871 877 ICR U-turn gas T/° C. 869 840 878 884 ProductU-turn gas T/° C. 857 827 865 871

Example

[0407] Welded ICR N3 was designed to test the effectiveness ofcombustion of CH4 by placing a slurry washcoat on the walls of thecombustion zone; this device operated without POx. The conversion of CH4was greater than 95% when the SMR side was running at 3:1 Steam: Carbonand 6 ms contact time. The results of N3 are shown in Tables 5 and 6.TABLE 5 Welded ICR N3 (direct CH4 combustion) results Air inlet gastemperature 160 157 162 (° C.) fuel inlet gas temperature 67 66 69 (°C.) Exhaust gas temperature 331 339 339 (° C.) Air inlet gas pressure(psig) 18.95 20.96 20.87 Fuel inlet gas pressure (psig) 17.88 19.5719.52 Exhaust gas pressure (psig) 7.93 9.37 9.14 Total fuel flow rate(SLPM) 0.958 CH4 0.958 NG 0.958 NG Fuel H2 content (%) 0 0 0 Fuel CH4 orNG content (%) 100% CH4 100% NG 100% NG Air flow rate (SLPM) 9.58 9.5810.5 % excess air 5 5 15 ICR contact time (ms) 5.2 5.2 4.8 Air pressuredrop (psi) 11.02 11.60 11.73 Fuel pressure drop (psi) 9.95 10.20 10.38Pressure gradient between air 0.535 0.695 0.675 and fuel channel (Psi)Combustion H2 conversion Na Na Na (%) Combustion CH4 conversion 96.896.8 100.0 (%) Comb. Selectivity to CO (%) 6.4 0 0 Combustion exhaustNOx Na Na Na (ppm) Combustion CO exhaust 5765 0 0 (ppm) Thermo loss (W)*251.7 260.5 265.2 SMR heat duty (W)^(c) 290.8 293.3 307.0 Combustionheat duty (W)^(d) 541 553.2 571.4 SMR reaction heat/ 0.54 0.53 0.54Combustion reaction heat SMR inlet gas temperature 337 339 339 (° C.)SMR outlet gas temperature 343 346 346 (° C.) SMR inlet pressure (psig)224.4 223.6 229.4 SMR outlet pressure (psig) 206.7 204.8 207.6 Pressuregradient between 202.65 199.73 204.2 SMR and fuel channel (psi) SMR CH4or NG flow rate 2.18 CH4 2.18 CH4 2.18 NG (SLPM) SMR steam flow rate(SLPM) 5.3 5.3 5.4 Molar steam-to-carbon ratio 3.03 3.03 2.98 SMRcontact time (ms) 6.0 6.0 5.9 SMR CH4 conversion 84.5 85.3 89.7 (GCBasis) (%) SMR Selectivity: CO (%) 59.3 58.5 56.1 SMR Average web 834816 817 temperature (° C.) Equilibrium conversion 820 824 851temperature (° C.) Equilibrium selectivity 812 807 792 temperature (°C.) SMR pressure drop (psi) 17.7 18.8 21.8 Average heat flux (W/cm2)16.9 17.1 17.9 Average reactor core 63.5 64.1 67.1 volumetric flux(W/cm3)^(ae) Endothermic Chamber heat 267 269 282 flux (W/cm3)^(f) Timeon Stream (Hrs) 22 37 63

[0408] TABLE 6 Temperature profile of N3 SMR reactant CH4 CH4 NG SMR S:C3.03 3.03 2.98 SMR CT 6.0 6.0 5.9 ICR fuel CH4 NG NG ICR CH4conversion/% 96.8 96.8 100 TC22(2″ above SMR zone) ° C. 686 694 693TC23(0.5″ above SMR zone) ° C. 734 745 744 TC24(0.06″ of 7″ SMR zone) °C. 724 726 720 TC25(0.32″ of 7″ SMR zone) ° C. 808 821 817 TC26(0.95″ of7″ SMR zone) ° C. 827 838 840 TC27(1.37″ of 7″ SMR zone) ° C. 815 826830 TC28(2.22″ of 7″ SMR zone) ° C. 804 814 819 TC29(2.94″ of 7″ SMRzone) ° C. 826 836 843 TC31(4.34″ of 7″ SMR zone) ° C. 809 793 791TC32(4.91″ of 7″ SMR zone) ° C. 833 816 818 TC47(6.31″ of 7″ SMR zone) °C. 834 815 816 ICR U-turn gas T/° C. 884 848 847 Product U-turn gas T/°C. 827 812 814

[0409] The integral 5-stream exchanger of N3 was evaluated forperformance, corresponding data are shown in Tables 7-9. The heatexchanger flux was calculated by summing the total heat gained by thecold streams and dividing by the heat exchanger core volume.

[0410] An energy balance for the exchanger was calculated by summing theheat gained by the cold streams and dividing by the heat lost by the hotstreams.

[0411] The residence times were calculated at the average measuredtemperature and pressure of the streams in the heat exchanger and arereported in milliseconds (ms). Residence time in each exchangermicrochannel is calculated as the total interior microchannel volume fora particular fluid divided by the actual volumetric flowrate. For eachfluid stream, the volumetric flowrate was an average over the inlet andoutlet conditions.

[0412] The temperatures of the fluids exiting the hot end of the heatexchanger could not be directly measured because of the integralreactor. Therefore, a thermocouple was placed in the metal web near thehot end of the heat exchanger and this temperature was used to estimatethe temperature of the cold streams (air, fuel, reactant) exiting theheat exchanger. The product and exhaust inlet temperatures to the hotend of the heat exchanger were estimated to be approximately 20° C. lessthan the measured U-turn gas temperature of the respective stream.

[0413] For the condition corresponding to second data column of Table 5,the welded ICR N3 has a heat exchanger flux of 14.2 W/cm³ and has lessthan 10% heat exchanger heat losses. The heat gained by the cold streamsand lost by the hot streams are approximately 255 W and 265 W,respectively. The internal heat exchanger volume is 17.95 cm3.

[0414] A parameter known as the Interstream Planar Heat Transfer AreaPercent (IPHTAP) was calculated. This parameter is defined as the ratioof area through which heat is transferred to neighboring channels withdifferent fluids to the total surface area in the channel. The totalsurface area exclusively includes rib, fins, surfaces that are notadjacent to another fluid-bearing channel, and surface area enhancers,if present. TABLE 7 N3 integral heat exchanger temperatures Units T airin ° C. 157 T fuel in ° C.  66 T air out ° C. 745 T fuel out ° C. 745 Texhaust in ° C. 828 T exhaust out ° C. 339 T reactant out ° C. 745 Treactant in ° C. 339 T product in ° C. 792 T product out ° C. 346

[0415] TABLE 8 N3 integral heat exchanger flowrates Flowrate (SLPM) Airflowrate 9.58 Fuel flowrate 0.958 Reactant CH4 flowrate 2.18 Reactantwater flowrate 5.3 SMR product flowrate 9.15 Exhaust flowrate 10.54

[0416] TABLE 9 N3 integral heat exchanger performance Residence time(ms) IPHTAP (%) Air stream 3.9 86 Fuel stream 49.1 94 Reactant stream24.5 97 Product stream 26.8 46 Exhaust stream 3.6 42

[0417] Welded ICR-M1

[0418] Installation/Startup

[0419] The microchannel ICR reactor system contains a series ofintegrated exchangers to preheat the process reactant, combustion airand combustion fuel. The integrated exchanger also cools the processproduct and combustion exhaust. The steams entering the device mayeither be at ambient conditions or at a slightly elevated temperature. Aseries of microchannel exchangers were optionally used to provideadditional preheat to the streams.

[0420] The process reactant was preheated to roughly 275 to 300 C. andthe combustion air was preheated to 150 to 170 C. using microchannelexchanger systems as described previously.

[0421] Combustion fuel was neat hydrogen to startup the device. Purehydrogen was selected as the startup fuel to avoid any coking potentialwithin the device, however it was anticipated that the device could alsobe started up with some amount of a hydrocarbon fuel in the mixture. Thefuel was not preheated externally to the device. Alternatively, the fuelcould have been preheated with either a microchannel exchanger or aconventional heat exchanger. The typical inlet fuel temperature asmeasured at the inlet to the microchannel ICR reactor system was 100 to125 C.

[0422] All inlet and outlet stream temperatures were measured using typeK thermocouples placed in the connecting tubes to the ICR reactor systemapproximately 5 to 10 cm from the inlet or outlet of the integrated heatexchanger on the ICR reactor system. Pressure transducers were added toeach of the inlet and outlet streams at similar locations.

[0423] The device was installed by connecting five Inconel 600 Swagelocktube fittings to the appropriate welded tube stubs on the ICR reactorsystem. Thermocouples were installed on the outer surface of the ICRreactor system along the length of the exchanger portion and the reactorportion. Additionally, several 0.02 inch thermocouples were insertedinto thermal wells built into the reactor and recuperator portions.

[0424] The reactant feed Brooks 5850e and 5851e series mass flowcontrollers, Omega model FMA-A23 mass flow meters, NoShok pressuretransducers model 1001501127 and 1003001127, Omega latching relaycontrollers model CNI 1653-C24, Swagelok variable pressure reliefvalves, thermal conductivity detector gas chromatograph, NOVA model 300CLD Chemiluminescent NO/NOx analyzer, etc were calibrated and verifiedfor proper operation. Flowrates were calibrated against a primarystandard calibrator, the Dry-Cal DC-2M Primary Flow Calibrator, whichwas calibrated and certified by BIOS International. Pressure transducerswere calibrated using a Fluke pressure calibrator model 718 1006 with aFluke 700P07 or 700P06 pressure module which were calibrated andcertified by Fluke. The gas chromatograph and NO/NOx analyzer werecalibrated against calibration gases blended and certified by PraxairDistribution Inc.

[0425] The ICR reactor system was pressure tested by first applying astatic pressure to the SMR reactant line while plugging the SMR productline. The applied pressure was 200 psig and was generated using anitrogen fluid. The pressure was left on this side of the device.Concurrently, the combustion side was pressurized to 75 psig while theSMR side was under pressure. The combustion side pressure may not exceedthe SMR side pressure during pressure testing to maintain the mechanicalintegrity of the device.

[0426] The leak rate did not exceed 0.5 psig in 15 minutes, and the ICRreactor system was ready for operation.

[0427] Catalyst reduction of the SMR and combustion sides was initiatedby first flowing nitrogen and hydrogen to the SMR and ICR reactantinlets. Typical SMR side flowrates were 2.5 SLPM nitrogen, and 0.25 SLPMhydrogen, while ICR side flowrates were 3.0 SLPM nitrogen and 0.3 SLPMhydrogen (both flows were 10% hydrogen, balance nitrogen). The ICR sideflows were entered through the fuel inlet and no fluid was entered intothe primary air inlet line. The microchannel exchangers were then usedto preheat the gases to the ICR reactor system to 120 to 150C. and holdtemperatures for 1 hour while not exceeding this range. The ICR reactorsystem heating rate was 2.5 to 5 C./min. The contact time during SMR andICR reduction was 19 and 17 milliseconds, respectively. Typically thecontact time was not allowed to exceed 20 milliseconds during reduction.

[0428] After the one-hour catalyst reduction process, the hydrogen onthe SMR process side and ICR combustion side was stopped. Nitrogenremains flowing on the SMR side at approximately 3.0 SLPM. The flowrateof nitrogen was equal to the total flowrate of SMR process reactantscorresponding to an 18 millisecond contact time. The 18 millisecondcontact time was the first flowrate of process reactants, and by settingthe nitrogen flowrate to an equivalent value there was a lesser changein temperature profile distribution in the ICR reactor system when thechange occurs from pure nitrogen during startup to operation of the ICRreactor system. Nitrogen on the ICR side remains on at roughly 2.0 SLPM.

[0429] Next the SMR side was pressurized to system operating pressure,160 to 170 psig outlet pressure, at 10-15 psig/min. While nitrogen wasflowing on the SMR side at a contact time of 18 milliseconds, thecombustion fluid flowrates were changed to heat the device to 600 C.Startup control was critical for uniform heating of the device andcontrol of heating rate (not to excel 5 C./min as described previously).Control was achieved by varying the flowrates of the hydrogen and airconcurrently while keeping them at 1:2.5 ratio which corresponds to 5%excess air. Increases in the fuel and air flowrates were offset byreductions in the nitrogen flowrate flowing in the fuel inlet line andthe primary air inlet line, respectively, to maintain a constantflowrate to the combustion side of the ICR reactor system. It wasimportant to maintain a roughly equal total flowrate of fluids in thecombustion side during startup to create a uniform temperature profile.If the combustion fluids flowrate drops by 50% or greater, then thefront of the catalyst section becomes much hotter than the end of thecatalyst section (+/−60 C. or higher). If the flowrate of the combustionfluids increases by 50% or greater then the back end of the catalystsection becomes much hotter than the front end of the catalyst section(+/−60 C. or higher). In both scenarios, the device will not maintainuniform heating and the heating rate will likely exceed the specified 5C./min.

[0430] To start the ICR combustion side heating, air was turned onthrough the primary air inlet line and hydrogen through the fuel inletline as described above while nitrogen also continues to flow into thesystem through the primary air inlet line and the fuel line. The initialflowrate of air and hydrogen was roughly 20% of the energy needed todrive the SMR reaction at 18 milliseconds and 6:1 steam-to-carbon, whichwas the first point at which the SMR process reactants will be turnedon. The fluids were changed by increasing the air and hydrogen flowrateswithin a minute of each other while maintaining their ratio at 5% excessair and turning down fuel and primary air line nitrogen to maintain aconstant overall flowrate. The constant overall flowrate roughlycorresponds to the total flowrate of combustion fuel and air required tooperate the SMR reaction at 18 ms at 600 C. By the time the devicereaches 600 C., the nitrogen will be reduced to zero.

[0431] If the air and hydrogen mixture does not light-off at reductiontemperatures, then the microchannel exchanger system was used to heatthe ICR reactor system until light-off was obtained. Typically thecombustion side lights off at reduction temperatures, 120-150C. Afterlight-off, the microchannel exchanger system was set to maintain theinlet temperatures required for the ICR reactor system. Additionally,although air was not fed with fuel through the fuel inlet inline in thistest, this could be done to assist in combustion conversion.

[0432] When the SMR side reaches roughly 400 C., hydrogen was turned onthe SMR reactant side at 15% of the total flowrate of steamcorresponding to a 6:1 steam-to-carbon ratio at 18 milliseconds. Thiswas roughly 400 sccm. Within one minute, the water pump on the SMR sidewas turned on to the liquid flowrate corresponding to a 6:1steam-to-carbon ratio at 18 milliseconds (2 ml/min). As the hydrogen andwater were fed to the SMR side, the nitrogen flowrate on the SMR sidewas correspondingly turned down to maintain the total stream at an 18 mscontact time.

[0433] The device continues to heat to 600 C. by changing the flowrateson the combustion side as described earlier. When the device reaches 600C., the combustion flows were increased in preparation for theinitiation of the SMR reaction and corresponding heat sink. The flowswere increased to roughly 500 sccm H2 through the fuel inlet line and1.3 SLPM air through the primary air inlet line, which was about 50% ofthe expected heat load of the SMR process side. Additionally, nitrogenwas decreased to roughly 500 sccm also through the primary air inletline and the fuel nitrogen was reduced to 500 sccm. Within a minute, theSMR methane was turned on to match a 6:1 steam-to-carbon ratio at 18milliseconds. First the nitrogen and then the hydrogen on the SMR sidewas then turned off and will not be used again until shutdown of the ICRreactor system.

[0434] The combustion flows were increased until the temperaturestabilizes at 600 C. (+40C., −0C.) in the reactor portion of the ICRreactor system. During this time the nitrogen on the combustion sidethrough the primary air inlet line and fuel line was turned off. Thedevice was then heated to the desired operating temperature for thereactor portion. The steam-to-carbon and contact time were varied to thedesired experimental conditions. As the steam-to-carbon and contact timewere varied, the heat load on the SMR side increases and the combustionside flows were increased to maintain the desired reactor temperature.The procedure for turning up the combustion side flows was air thenfuel, while turning down combustion side flows was fuel than air.

[0435] For the device, the temperature of the reactor portion of the ICRwas heated to at least 800 C. before reducing the steam-to-carbon to 3:1or below. During the transition from startup conditions to operatingconditions, the procedure for changing conditions on the SMR processside was to increase water flowrate before increasing SMR processhydrocarbon flowrate (i.e. going to a higher steam-to-carbon ratio thenback to the desired steam-to-carbon ratio).

[0436] Additionally, hydrocarbon feeds may be added to the combustionfuel during this time or earlier with a corresponding correction to theair flowrate to maintain proper fuel to air ratio. The procedure forthis process was to first increase the combustion primary air by theflowrate required to maintain the desired excess air ratio, then turn onthe hydrocarbon flowrate and then turn down the hydrogen flowrate by thesame energy output that the hydrocarbon flowrate was turned up.

[0437] The shutdown process was the reverse of the start-up process. Theemergency shutdown procedure and the control strategies were the same asdiscussed previously.

[0438] Results

[0439] The Welded ICR-M1 was tested over a wide range of processconditions, including 12-20 bar average SMR pressure, 4-18 ms SMRcontact time (900000-200000 hr⁻¹ GHSV), and steam-to-carbon ratios from6:1 to 1.25:1, yielding 800-850° C. equilibrium conversion andselectivity performance. Combustion performance was evaluated usinghydrogen fuel, and hydrogen/hydrocarbon fuel mixtures containing 5-10%CH₄ or natural gas and 8% CO₂. In addition, combustion performance using5-50% excess air was evaluated. The M1 reactor was operated continuouslyfor over 300 hours with no decrease in process performance.

[0440] Web temperatures were measured inside thermowells extended 1 mmdeep beyond the perimeter metal into the metal web between the SMR andcombustion flows. FIG. 32 shows thermocouple locations and a typicalmeasured temperature profile at conditions corresponding to an 840° C.SMR equilibrium selectivity and conversion at a 6 ms SMR contact time.The temperature profile peaked in the center of the device and thendecreased down the length of the reactor.

[0441] The detailed results of a few selected tests using the weldeddevice M1 are shown in Table 10. As shown in the table, steam-to-carbonratios as low as 1.25:1 were evaluated and surprisingly the device didnot produce discernable quantities of coke. The device was operated upto 20 bar absolute pressure and evaluated with methane in the combustionfuel stream up to 10%. Note that metal temperatures are maintained below950° C. along the entire reactor zone even when near stoichiometriccombustion mixtures were used. NO_(x), values in the combustion effluentsurprisingly never exceeded 5 ppm, even when the maximum reactortemperature was raised to 925 C.

[0442]FIG. 33 shows a simplified overview of the types of SMR conditionsover which the welded device M1 was tested during 300 hours ofcontinuous operation. No evidence of SMR deactivation was seen duringthe entire 300 hours of operation. FIG. 34 shows combustion performancedata for the first 200 hours. Note the consistently high conversions andlow NO_(x), levels from microchannel catalytic combustion. The presenceof some CO in the combustion products suggests that some portion of thecombustion occurred in the gas phase (non-catalytic). It should also benoted that the inadvertent omission of the flow stabilization porousinsert from one of the fuel channels caused a mal-distribution of fuelbetween the two channels in the welded device M1. This is consistentwith the observed partial combustion hydrogen conversion for 5% excessair overall (one channel runs fuel rich, the other fuel lean, leading touncombusted fuel in one channel and air in the other), and the completefuel conversion observed in tests using 25-50% excess air.

[0443] The welded ICR devices M1 and M2 (as well as the bonded ICRdevice of Example 2) each included a porous flow stabilization insert ineach fuel channel immediately upstream of the first point of airinjection. These porous inserts were made from rectangular pieces ofFeCrAlloy foam (˜95 pores per inch) measuring 0.7 mm thick, 13 mm long(flow direction) by about 5 mm wide.

[0444] The flow stabilization inserts prevented combustion flowinstabilities. One example of combustion flow instability can occurduring hydrogen combustion where a flame may travel from the point ofair and fuel mixing to a point further upstream in the fuel line due tothe high flame speeds of hydrogen flames. In addition, because thevolumetric fuel flows are generally much smaller than the volumetric airflows, it is possible for air to travel upstream on one side of the fuelchannel and combust in the fuel channel while combustion products traveldownstream on the other side of the same channel. This would cause heatto be added upstream of the desired location in an uncontrolled fashion.Such instabilities are more likely when air and fuel streams areundiluted, creating local stoichiometric mixtures where they are firstmixed. Thus there is a need to stabilize the combustion flowsimmediately upstream of the first point of mixing of fuel and air. Theflow stabilization inserts prevent such undesirable combustion behaviorby distributing the fuel flow over the entire fuel channel just prior tomixing with air, increasing the local velocity of the fuel, andproviding high surface area small diameter passageways to quench thecombustion flame intermediate species (i.e. free radicals) whichpropagate combustion. This flow stabilization feature could befabricated in any of a variety of different forms by those skilled inthe art.

[0445] In the bonded ICR device of Example 1 the combustion flowstabilization function was provided by narrowing the fuel channel to0.25 mm until the point immediately upstream of the first point of airinjection, where the channel widened to the full 0.66 mm height. Thenarrow fuel channel passageway was located immediately adjacent to thewall in which the air injection orifices were located. The fuel channelwidened in a single step change away from the wall containing the airinjection orifices, effectively cutting 0.41 mm deep into the wallopposite the air injection orifices.

[0446] The narrow fuel channel in the bonded ICR device of Example 1provided combustion flow stabilization in much the same way as the flowstabilization inserts of the welded ICR device M1. Specifically, thenarrow fuel passageway increased the local velocity of the fuel andprovided a small diameter passageway to quench combustion flameintermediate species (i.e. free radicals) which propagate combustionflames. Multiple parallel narrow passageways could also be used toprovide the same function.

[0447] Combustion and catalytic combustion in microchannels isfacilitated by the excellent heat transfer provided by flow inmicrochannels, allowing more flammable mixtures (i.e.near-stoichiometric or low excess air) to be used and providingcontinuous preheat of combustion reactants immediately upstream of thecombustion reaction zone. These two characteristics of microchannelcombustion (use of near-stoichiometric mixtures and continuous reactantpreheat) have a stabilizing and promoting effect on the combustion andcatalytic combustion of more difficult to combust fuels, such asmethane. For this reason, combustion or catalytic combustion can beperformed in microchannels at contact times much lower than conventionaltechnology, allowing intensified heat delivery in a compact reactor.

[0448] The device of Example X(1) the welded ICR device M1 was carefullycut open after being shut down to look for carbonaceous deposits.Despite operation at conditions which are known to be coke prone inconventional SMR reactors, No carbon (coke) formation was seen in thecombustion channels and very little coke formation was seen on theprocess (SMR) catalyst and in the process channels of the device ofExample X(1) the welded ICR device M1. In fact, except for theupstream-most inch or so, the catalyst was completely coke free, as wasthe U-turn area, despite several obvious dead-flow zones. It is thoughtthat many of the free-radical intermediates which play a role in theformation of coke from hydrocarbons are essentially “quenched” by theproximity of the wall to the gas stream., much like homogeneouscombustion reactions are quenched by reducing the diameter of thecombustion walls below a given diameter.

[0449] After about 150 hours of testing the temperature was reduced to˜600° C. and the SMR pressure and load were removed for 8 hours duringchange out of some of the demonstration equipment required toinvestigate higher pressure operation and shorter contact times.Surprisingly, after this changeover when the SMR load was re-applied andthe pressure increased to 20 bar the SMR approach to equilibrium changedfrom −60° C. to about −35° C. (compare second and third columns in Table10. It is thought that the pressure cycle may have caused better contactbetween the wall and the catalyst, since the change was accompanied by asignificant increase in the fraction of combustion heat which isabsorbed by the SMR reaction. FIG. 35 shows SMR performance data beforethe pressure cycle, and FIGS. 36-37 show SMR performance data after thepressure cycle. TABLE 10 Selected results from operation of the weldedICR device M1. Before After Lowest H₂ fuel cycling in cycling S:C, 20Lowest only pressure pressure atm S:C, NG Time on stream (hours) 26 136168 165 182 Air inlet gas temperature 159 155 155 155 155 (° C.) Fuelinlet gas temperature 102 112 113 112 115 (° C.) Combustion U-turn gas787 882 887 892 870 temp. (° C.) Exhaust gas temperature 317 363 352 352354 (° C.) Air inlet pressure (Pa/10⁵) 2.21 2.91 2.80 2.79 2.81 Fuelinlet pressure (Pa/10⁵) 1.85 2.33 2.29 2.27 2.30 Exhaust outlet pressure1.14 1.16 1.16 1.15 1.14 (Pa/10⁵) Total fuel flow rate (SLPM) 3.16 3.413.12 3.12 3.09 Fuel H₂ content (%) 100 85 85 85 85 Fuel CH₄ content (%)0 7 7 7 7(NG)^(c) Fuel CO₂ content (%) 0 8 8 8 8 Air flow rate (SLPM)7.9 11.5 10.5 10.5 10.4 % excess air (based on inlet) 5 25 25 25 25 %excess air (measured) 2.4 24 26 25 26 Combustion contact time 5.0 3.84.1 4.1 4.2 (ms)^(a) Air pressure drop (Pa/10⁵) 1.06 1.75 1.63 1.64 1.66Fuel pressure drop (Pa/10⁵) 0.71 1.17 1.12 1.12 1.16 Combustion H₂conversion 87.4 99.2 99.6 99 99.3 (%) Combustion CH₄ conversion — 100100 100 100 (%) Comb. selectivity to CO₂ — 72.9 76.9 74 84.4 (%) Comb.(carbon out)/(carbon — 0.93 1.06 1.01 1.04 in) Combustion exhaust NO_(x)0.4 4.4 3.5 2.9 4.6 (ppm) SMR inlet gas temperature 288 288 285 288 286(° C.) SMR U-turn gas temp. (° C.) 762 822 829 934 822 SMR outlet gastemperature 295 308 301 302 303 (° C.) SMR inlet pressure (Pa/10⁵) 13.5913.83 14.04 20.31 14.32 SMR outlet pressure (Pa/10⁵) 11.75 12.11 12.3219.14 12.52 SMR average pressure 12.7 13.0 13.2 19.7 13.4 (Pa/10⁵) SMRpressure drop (Pa/10⁵) 1.8 1.7 1.7 1.2 1.8 SMR to comb. differential11.2 11.2 11.5 18.0 11.7 (Pa/10⁵) SMR CH₄ flow rate (SLPM) 2.91 2.912.91 3.87 2.84(NG)^(b) SMR steam flow rate 5.86 5.86 5.86 4.86 5.86(SLPM) Molar Steam to Methane 2.0 2.0 2.0 1.26 2.0 Ratio SMR contacttime (ms) 6.0 6.0 6.0 6.0 6.0 CH₄ conversion (GC Basis) 59.9 71.4 78.559.0 78.3 (%) Selectivity: CO (%) 68.7 77.3 74.1 82.8 73.4 SMR (carbonout)/(carbon 1.10 1.14 0.96 0.78 0.96 in) Average reactor web temp. 775835 843 846 835 (° C.)^(c) Equilibrium conversion T 760 804 834 846 833(° C.) Equilibrium selectivity T 807 867 841 872 836 (° C.) SMR rxn.heat/comb. rxn. 0.55 0.53 0.64 0.64 0.63 heat^(d) Average area heat flux16.2 19.7 21.5 21.8 20.9 (W/cm²) Reactor core volumetric flux 60.8 73.880.7 81.8 78.5 (W/cm³) Endothermic reaction 319 387 424 429 412 chamberflux (W/cm³) Temperature on skin 109 mm from 834 890 897 892 899 u-turn,product side (° C.) Temperature on skin 163 mm from 831 869 863 858 871u-turn, product side (° C.) Temperature on skin 173 mm from 614 637 633630 635 u-turn, product side (° C.) Temperature on skin 368 mm from 422446 438 438 440 u-turn, product side (° C.) Temperature in web at u-turn(° C.) 761 820 827 831 819 Temperature in web 47 mm from 789 851 858 861850 u-turn (° C.) Temperature in web 106 mm from 844 911 918 914 914u-turn (° C.) Temperature in web 141 mm from 495 514 513 510 514 u-turn(° C.) Temperature in web 163 mm from 838 876 871 865 879 u-turn (° C.)Temperature in web 170 mm from 541 508 844 839 849 u-turn (° C.)Temperature in web at u-turn, 787 882 887 892 870 combustion side (° C.)Temperature on skin 109 mm from 858 922 926 921 926 u-turn, combustionside (° C.) Temperature on skin 163 mm from 847 884 877 871 886 u-turn,combustion side (° C.) Temperature on skin 272 mm from 614 637 634 631636 u-turn, combustion side (° C.) Temperature on skin 368 mm from 438462 457 456 459 u-turn, combustion side (° C.) Temperature on skin 496mm from 256 272 268 267 269 u-turn, combustion side (° C.)

[0450] Some error was found to be associated with dry product exit flowmeasurements due to changes in the dry test meter calibration, thoughtto be due to water accumulation in the test meter. This, combined withminor errors in mass flow controller and GC calibrations, contributed tocarbon balance errors in the range of ±12%.

[0451] Welded ICR-M2

[0452] Installation/Startup

[0453] The installation of M2 follows the same procedure as M1 with thefollowing exceptions:

[0454] The system was pressure tested at 300 psig on the SMR processside and 60 psig on the combustion side.

[0455] The SMR process inlet was heated to 230 to 300C.

[0456] The combustion primary air inlet preheat was 150C. to 170C.initially, but at approximately 25 hours on stream the preheat was lost,reducing the primary air inlet temperature to 30 to 40C. with noapparent change in performance of the combustion side or the SMR processside.

[0457] The combustion side fuel inlet was preheated to 60 to 95C.

[0458] The combustion side catalyst was not reduced. It was used withoutreduction, and lit-off at roughly 50C.

[0459] The combustion side light-off was achieved using a fuel richcondition, which was tested to determine if fuel rich or fuel leancombustion reactant feeds offered better startup control. The combustionfluids were initiated in the following manner to achieve propertemperatures for SMR catalyst reduction. The SMR catalyst reductiontemperature was roughly 120 to 150 C. The ICR reactor system waspreheated by using the integrated combustion portion of the reactor. Theprocess was initiated by increasing SMR side nitrogen flowrate 2.5 SLPM,and the hydrogen flow to 250 sccm. Both nitrogen and the 10% hydrogenwere left on during the heatup of the ICR reactor system and one hourreduction time for the SMR. This corresponds to a contact time of 19milliseconds, and the contact time was not allowed to exceed 20milliseconds during reduction. Nitrogen was then fed to the combustionside through the primary air inlet at roughly 1.0 SLPM, and the fuelinlet line at roughly 500 sccm. The air was then blended with theprimary air line nitrogen and fed at a rate of 1.5 seem. Then thehydrogen was started on the combustion fuel inlet at a flowrate of 600seem. The hydrogen lit off at roughly 50C. The heat released fromcombustion heats the ICR reactor system. The heat up rate was roughly 5C./minute. Startup control was important for appropriate catalystreduction to achieve a near isothermal (+/−30 C.) temperaturedistribution along the length of the 7 inch catalyst section in the ICRreactor system. Control was achieved by varying the flowrates of thehydrogen and air concurrently while keeping them at a 1.2:1 ratio whichcorresponds to −50% excess air. Increases in the fuel and air flowrateswere offset by reductions in the fuel and primary air line nitrogenflowrates, respectively, to maintain a constant flowrate to thecombustion side of the ICR reactor system. It was important to maintaina roughly equal total flowrate of fluids in the combustion side duringstartup to create a uniform temperature profile. If the combustionfluids flowrates drops by 50% or greater, then the front of the catalystsection becomes much hotter than the end of the catalyst section (+/−60C. or higher). If the flowrate of the combustion fluids increases by 50%or greater then the back end of the catalyst section becomes much hotterthan the front end of the catalyst section (+/−60 C. or higher). In bothscenarios, the catalyst does not properly reduce. Once the ICR reactorsystem reaches 120 to 150C., the one hour reduction time begins.Following the one hour SMR reduction time, the device is heated asdescribed in M1. System operating pressure was both 160-170 psig and260-270 psig at the SMR process outlet and was changed betweenalternatively.

[0460] Results

[0461] The welded ICR device M2 was successfully operated over a widerange of process conditions, including 12-20.5 bar average SMR pressure,3.8-18 ms SMR contact time (947000-200000 hr⁻¹ GHSV), andsteam-to-carbon ratios from 6:1 to 2:1, yielding 825-870° C. equilibriumperformance. Combustion performance was evaluated using hydrogen fuel,and hydrogen/hydrocarbon fuel mixtures containing 5-7% CH₄ or naturalgas and 8% CO₂. In addition, combustion performance using 5-10% excessair was shown. In all, the reactor was operated continuously for over350 hours with no decrease in process performance.

[0462] The welded ICR device M2 was designed with 12 jets per channel(versus 9 in welded ICR device M1) with the last jet only 33 mm from theend of the reaction channel. The increased number of jets reduced theobserved combustion air pressure drop relative to the 9 jet design. Thejets were also more uniformly spread out over the length of the reactionzone, producing a more uniform temperature gradient in the reactor andbetter SMR performance at a given reactor temperature.

[0463] The detailed results of a few selected tests using the welded ICRdevice M2 are shown in Table 11. In Table 11 it can be seen thatessentially complete hydrogen combustion was achieved in this reactorwith only 5% excess combustion air. NO_(x), levels in the dry combustioneffluent were consistently below 2 ppm, and never exceeded 5 ppm. Theresults in Table 11 also include volumetric fluxes of 112-116 W/cc,reached during operation of the welded ICR device M2 at 2:1 steam:C andpressures (average) of 18-20.5 bar while producing syngas equilibratedat 830-840° C. The corresponding SMR space velocity for theseperformance data is 947000 hr⁻¹ (3.8 ms contact time). SMR performanceis also excellent at longer SMR contact times, most notably at 5 ms and21 bar (2:1 steam:C), for which syngas was produced with an equilibriumcomposition corresponding to an apparent temperature of 870° C. Atypical temperature profile for the welded ICR device M2 is shown inFIG. 38.

[0464] Other performance data for the welded ICR device M2 are shown inFIGS. 39-42. The SMR reactor performed as an equilibrium reactor for SMRcontact times as low as 5 ms, both at 13 bar (FIG. 40) and 20 bar (FIG.41) The equilibrium approach temperature appears to begin to divergefrom the measured final web temperature as SMR contact time is decreasedbelow 6 ms (FIGS. 40-41) for this device. These results show theeffectiveness of distributed air combustion in obtaining high area heatfluxes (15 -31 W/cm²) while avoiding hot spots and SMR catalystdeactivation. TABLE 11 Selected results from operation of the welded ICRdevice M2. H₂ fuel Low P, low Highest High P High P only XS air fluxhigh flux highest T Time on stream (hours) 19 26 43 45 46 Air inlet gastemperature 150 95 32 32 31 (° C.) Fuel inlet gas temperature 74 67 6059 60 (° C.) Combustion U-turn gas 878 920 955 947 945 temp. (° C.)Exhaust gas temperature 286 298 346 342 316 (° C.) Air inlet pressure(Pa/10⁵) 2.05 2.34 2.97 2.92 2.70 Fuel inlet pressure (Pa/10⁵) 1.78 2.032.50 2.46 2.30 Exhaust outlet pressure 1.19 1.20 1.27 1.28 1.25 (Pa/10⁵)Total fuel flow rate (SLPM) 2.90 3.52 4.82 4.68 4.08 Fuel H₂ content (%)100 89 87 87 87 Fuel CH₄ content (%) 0 5 7 7 7.0 Fuel CO₂ content (%) 06 6 6 6.0 Air flow rate (SLPM) 7.26 9.6 14.5 14.1 12.3 % excess air(based on inlet) 5 5 10 10 10 % excess air (measured) 7 5 5 5 5Combustion contact time 5.4 4.2 2.9 2.9 3.4 (ms)^(a) Air pressure drop(Pa/10⁵) 0.85 1.14 1.70 1.65 1.45 Fuel pressure drop (Pa/10⁵) 0.59 0.831.23 1.19 1.05 Combustion H₂ conversion 99.7 99.8 99.5 99.5 99.6 (%)Combustion CH₄ conversion — 41.4 34.0 25.3 34.7 (%) Comb. selectivity toCO₂ — 84.0 55.0 35.2 66.9 (%) Comb. (carbon out)/(carbon — 0.936 0.860.85 1.13 in) Combustion exhaust NOx 0.7 0.8 1.9 1.0 1.8 (ppm) SMR inletgas temperature 258 239 265 266 249 (° C.) SMR U-turn gas temp. (° C.)813 856 859 859 874 SMR outlet gas temperature 277 266 294 294 270 (°C.) SMR inlet pressure (Pa/10⁵) 14.04 14.18 19.00 21.35 20.93 SMR outletpressure (Pa/10⁵) 12.59 12.66 17.00 19.69 19.62 SMR average pressure13.3 13.4 18.0 20.5 20.3 (Pa/10⁵) SMR pressure drop (Pa/10⁵) 1.4 1.5 2.01.7 1.3 SMR to comb. differential 11.8 11.8 16.1 18.7 18.5 (Pa/10⁵) SMRCH₄ flow rate (SLPM) 2.91 2.91 4.59 4.59 3.49 SMR steam flow rate 5.865.86 9.23 9.23 6.98 (SLPM) Molar Steam to Methane 2.0 2.0 2.0 2.0 2.0Ratio SMR contact time (ms) 6.0 6.0 3.8 3.8 5.0 CH₄ conversion (GCBasis) 75.3 83.4 72.1 70.0 77.0 (%) Selectivity: CO (%) 69.8 75.0 69.569.0 74.1 SMR (carbon out)/(carbon 1.17 0.86 1.10 1.10 1.16 in) Averagereactor web temp. 839 881 881 879 890 (° C.)^(b) Equilibrium conversionT 825 863 838 841 871 (° C.) Equilibrium selectivity T 816 851 831 836869 (° C.) SMR rxn. heat/comb. rxn. 0.660 0.646 0.645 0.652 0.623heat^(c) Average heat flux (W/cm²) 20.5 22.9 31.0 30.1 25.4 Reactor corevolumetric flux 76.9 86.0 116.3 112.7 95.1 (W/cm³) Endothermic reaction404 452 611 592 499 chamber flux (W/cm³) Temperature in web at u-turn (°C.) 849 808 849 859 858 Temperature in web 44 mm from 913 870 913 903899 u-turn (° C.) Temperature in web 104 mm from 877 828 877 887 884u-turn (° C.) Temperature in web 110 mm from 873 825 873 886 882 u-turn(° C.) Temperature in web 137 mm from 838 800 838 858 855 u-turn (° C.)Temperature in web 143 mm from 822 795 822 845 841 u-turn (° C.)Temperature in web 161 mm from 797 768 797 816 813 u-turn (° C.)Temperature in web 170 mm from 787 769 787 800 797 u-turn (° C.)Temperature in skin 110 mm from 842 802 842 864 861 u-turn, combustionside (° C.) Temperature in skin 178 mm from 761 735 761 777 775 u-turn,combustion side (° C.) Temperature in skin 260 mm from 473 468 473 491491 u-turn, combustion side (° C.) Temperature in skin 374 mm from 360364 360 379 379 u-turn, combustion side (° C.) Temperature in skin 504mm from 209 219 209 216 215 u-turn, combustion side (° C.)

We claim:
 1. A method of conducting simultaneous exothermic andendothermic reactions, comprising: flowing a fuel into a microchannelcombustion chamber; adding an oxidant to the combustion chamber suchthat the oxidant oxidizes the fuel and temperature in the combustionchamber increases from the front of the combustion chamber to the back;providing an endothermic reaction composition in an endothermic reactionchamber that is disposed adjacent to the combustion chamber, wherein theendothermic reaction chamber and the combustion chamber are separated bya thermally conductive wall; wherein the endothermic reactioncomposition endothermically reacts to form products.
 2. The method ofclaim 1 wherein and temperature in the combustion chamber increasessubstantially monotonically from the front of the combustion chamber tothe back.
 3. The method of claim 1 wherein the oxidant comprises air andthe combustion results in less than 10 ppm NOx.
 4. The method of claim 1wherein the endothermic reaction comprises steam reforming.
 5. Themethod of claim 4 further comprising a step of prereforming a mixture ofhydrocarbons to form methane and using the resulting methane in theendothermic reaction composition.
 6. The method of claim 1 wherein themethod is conducted in an integrated combustion reactor (ICR) that hasone free end and a non-free end; wherein the non-free end of the ICRcontains connections for fuel, oxidant and exhaust.
 7. The method ofclaim 1 further comprising the step of partially oxidizing a fuel priorto passage into the combustion chamber.
 8. An integrated reactor,comprising: a exothermic microchannel comprising an exothermic reactioncatalyst; an endothermic reaction microchannel adjacent the exothermicmicrochannel and comprising an endothermic reaction catalyst, theendothermic reaction catalyst having a length, in the direction of flow,of at least 10 cm; and a wall separating the exothermic reactioncatalyst and the endothermic reaction catalyst.
 9. The integratedreactor of claim 8 wherein the endothermic reaction microchannel has aheight (the dimension perpendicular to flow and defining the shortestdistance from the center of the endothermic reaction microchannel to thecombustion microchannel) of 0.5 mm or less.
 10. The integrated reactorof claim 8 wherein at least one wall defining the combustionmicrochannel contains apertures connecting gas flow between thecombustion microchannel and an adjacent air channel.
 11. The integratedreactor of claim 8 wherein a gap of at least 0.2 mm exists between awall of the endothermic reaction microchannel and a surface of theendothermic reaction catalyst.
 12. The integrated reactor of claim 8wherein the exothermic reaction catalyst is a combustion catalyst. 13.An integrated reactor, comprising: a stack of at least two microchannelswherein at least one of the at least two microchannels comprises aremovable catalyst insert and a catalyst door.
 14. A method ofconducting an endothermic reaction in an integrated combustion reaction,comprising: passing an endothermic reaction composition into at leastone endothermic reaction chamber, passing a fuel and an oxidant into atleast one exothermic reaction chamber wherein the fuel and oxidant eachhave a contact time in the combustion chamber of 20 milliseconds orless, wherein the exothermic reaction chamber comprises at least oneexothermic reaction chamber wall that is adjacent at least oneendothermic reaction chamber, wherein the endothermic reaction chambercomprises an endothermic reaction catalyst in contact with at least theat least one endothermic reaction chamber wall that is adjacent at leastone exothermic reaction chamber, transferring heat from the at least oneexothermic reaction chamber into the at least one endothermic reactionchamber at a rate of at least 5 W/cm² as based on the internal area ofthe endothermic reaction chamber.